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`US 6,771,342 B1
`(10) Patent N0.:
`(12) United States Patent
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`Hirakata et al.
`(45) Date of Patent:
`Aug. 3, 2004
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`USOO6771342B1
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`(54) LIQUID CRYSTAL DISPLAY DEVICE AND
`DISPLAY DEVICE
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`(75)
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`( * ) Notice:
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`Inventors: Yoshiharu Hirakata, Kanagawa (JP);
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`gfikesm. 1\‘I{1sh1, KgagTavlza 01:1);
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`unpe,‘ amaza ’
`0 yo (
`)’
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`Takeshl Fukunaga> Kanagawa (JP)
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`(73) ASSIgHeei SemlCOHduCtOF Energy LabOratOry
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`C0-, Ltd-, Kanagawa-ken (JP)
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`Subject to any disclaimer, the term of this
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`patent is extended or adjusted under 35
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`U~S~C~ 154(b) by 0 daYS-
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`(22)
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`(30)
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`(51)
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`(21) Appl. No.: 08/811,152
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`Filed:
`Mar. 4, 1997
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`Foreign Application Priority Data
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`Mar. 5, 1996
`(JP)
`............................................. 8—078346
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`Mar. 26, 1996
`(JP)
`8—096318
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`Apr. 9, 1996
`............................................. 8—113166
`(JP)
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`Int. Cl.7 ....................... G02F 1/1343; G02F 1/136;
`G02F 1/1333
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`......................... 349/141, 349/43, 349/110,
`349/138
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`(58) Field of Search ............................. 349/42, 43, 110,
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`349/111, 138, 141, 257/59, 72
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`(52) US. Cl.
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`(56)
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`References Cited
`U.S. PATENT DOCUMENTS
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`3,774,989 A
`
`5,055,899 A
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`5,339,181 A
`
`
`............. 350/160 LC
`11/1973 Takahashi
`
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`
`
`....... 357/237
`10/1991 Wakai et a1.
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`.................... 359/59
`8/1994 Kim etal.
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`
`............ 437/42
`5/1996 Yamazaki et a1.
`5,521,107 A
`7/1997 Sakamoto ................... 257/764
`5,650,664 A
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`12/1997 Sano et al.
`................. 349/139
`5,694,188 A
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`giggggé 2 : 3133: ganagawa 6: ai~ ~~~~~~~~~~~~ gig/:8
`anagawae a.
`.....
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`5,814,834 A *
`9/1998 Yamazaki et al.
`............ 257/59
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`5,815,226 A *
`9/1998 Yamazaki et al.
`.......... 349/111
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`5,897,345 A
`4/1999 Uochi
`........................ 438/151
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`6,013,928 A
`1/2000 Yamazaki et al.
`...... 257/347
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`6,133,620 A
`10/2000 Uochi
`........................ 257/649
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`6,160,600 A
`12/2000 Yamazaki et al.
`.......... 349/138
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`FOREIGN PATENT DOCUMENTS
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`4—163528
`6/1992
`*
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`07—036058
`2/1995
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`JP
`JP
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`* cited by examiner
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`Primary Examiner—Tarifur R. Chowdhury
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`(74) Attorney, Agent, or Firm—Fish & Richardson PC
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`ABSTRACT
`(57)
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`In a liquid crystal display device Which performs image
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`display by controlling a liquid crystal layer by a lateral
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`electric field that is parallel With a substrate,
`the lateral
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`electric field is formed by a black matrix and a pixel
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`electrode. That is, a common electrode and a black matrix
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`are commonized Which are separately provided convention-
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`ally. Further, a storage capacitor is formed in an area Where
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`the black matrix and a pixel line coextend With a third
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`interlayer insulating film interposed in between. Since the
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`storage capacitor is formed by using all the area Where a
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`thin-film transistor is covered With the black matrix, suffi-
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`cient capacitance can be secured even if the Widths of
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`electrodes Wiring lines are reduced in the future.
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`46 Claims, 11 Drawing Sheets
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`1
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`LIQUID CRYSTAL DISPLAY DEVICE AND
`DISPLAY DEVICE
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`US 6,771,342 B1
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`BACKGROUND OF THE INVENTION
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`1. Field of the Invention
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`The present invention relates to a liquid crystal display
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`device in which control is made by semiconductor devices
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`that are formed by using a crystalline silicon film. The
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`invention can be applied to MIM, passive matrix, active
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`matrix, and other liquid crystal display devices.
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`2. Description of the Related Art
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`In recent years, techniques of forming thin-film transistors
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`(TFTs) on an inexpensive glass substrate have been devel-
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`oped at high speed. This is because of an increased demand
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`for higher-resolution liquid crystal display devices as dis-
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`play media of multimedia.
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`For example, in an active matrix display device, thin-film
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`transistors are provided for millions of respective pixels
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`arranged in matrix form and charge to enter or exit from each
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`pixel electrode is controlled by the switching function of the
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`thin-film transistor. Image display is performed by control-
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`ling the amount of light that passes through a liquid crystal
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`panel by changing the electro-optical characteristic of a
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`liquid crystal in accordance with an image signal supplied
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`from a data line. Since a voltage applied to the liquid crystal
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`is desired to be constant until the next writing, the image
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`signal potential is held by a storage capacitor for a given
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`As a driving method of the above type of liquid crystal
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`display device, the IPS mode now attracts much attention in
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`which a parallel electrode structure is employed and the
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`device is driven by controlling an electric field that
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`parallel with a substrate.
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`A liquid crystal display device driven by the IPS mode is
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`featured by a large viewing angle, high contrast, etc. and has
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`thin-film transistors, gate lines, data lines (source lines),
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`pixel electrodes, a common line, and a common electrode
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`extending therefrom in a pixel area on the same substrate.
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`In particular, in the IPS mode in which a lateral electric
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`field is controlled, each pixel electrode is interposed
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`between common electrodes that are arranged parallel with
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`the pixel electrode so that an electric field applied to the
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`pixel electrode does not influence other pixels etc. Since a
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`certain area should be secured for those electrodes, the open
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`area ratio (aperture ratio), i.e., the ratio of an area which
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`transmits light for display, of the pixel area is lowered.
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`Further, to secure a sufficient charge holding time, a liquid
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`crystal display requires a structure in which a storage
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`capacitor is added to a pixel electrode. This is not limited to
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`liquid crystal displays driven by the IPS mode, but appli-
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`cable to conventional liquid crystal display devices.
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`However, the provision of electrodes for forming storage
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`capacitors (capacitance electrodes) could be a factor of
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`lowering the open area ratio (aperture ratio). In view of this,
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`a technique has been proposed in which capacitance elec-
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`trodes formed in the same laser as gate lines also serve as a
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`black matrix (US. Pat. No. 5,339,181). However, this tech-
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`nique still has a problem that the capacitance electrodes
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`cannot fully serve as the black matrix because of a problem
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`relating to parasitic capacitance.
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`Another technique has been proposed in which a storage
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`capacitor as mentioned above is formed by utilizing an area
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`where a pixel electrode and a common electrode overlap
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`with each other (Japanese Unexamined Patent Publication
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`No. Hei. 7-36058). However, it is expected that as the degree
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`of electrode miniaturization increases,
`the area where to
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`form a storage capacitor becomes smaller, making it impos-
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`sible to secure a necessary and sufficient capacitance. If it is
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`attempted to form a storage capacitor having a necessary
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`capacitance, the area occupied by the capacitance element
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`will necessarily become large, to lower the open area ratio
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`is
`Conventionally,
`the light quantity of a backlight
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`increased to compensate for a low open area ratio (low
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`aperture ratio), to thereby secure necessary brightness of a
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`screen, However, because of increased power consumption,
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`this is a large obstacle to incorporation of a liquid crystal
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`display device into devices that are required to be portable.
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`As described above, a technique is now desired which can
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`secure a necessary storage capacitance without sacrificing
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`the open area ratio (aperture ratio). To improve the open area
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`ratio (aperture ratio) with the IPS mode, it is desired that the
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`electrode width be reduced to less than 1—2 pm. Although
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`submicron or even finer patterning techniques have already
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`been established, they are now encountering difficulties in
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`mass production,
`resulting in delay of technological
`progress.
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`SUMMARY OF THE INVENTION
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`An object of the present invention is, therefore, to propose
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`a technique for forming storage capacitors which well
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`matches fine processing technologies, as well as to provide
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`a technique for forming a pixel area having a large open area
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`ratio (large aperture ratio).
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`According to one aspect of the invention, there is pro-
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`vided a liquid crystal display device comprising a first
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`substrate comprising a pixel electrode and a common elec-
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`trode both being made of a conductive material, the common
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`electrode being a black matrix; a second substrate opposed
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`to the first substrate; and a liquid crystal held between the
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`first and second substrates, and driven by an electric field
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`formed between the pixel electrode and the common
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`electrode, the electric field having a component parallel with
`the substrates.
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`According to another aspect of the invention, there is
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`provided a liquid crystal display device comprising a first
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`substrate comprising a second interlayer insulating film
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`made of an organic resin material or an inorganic material;
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`a pixel line and a pixel electrode extending from the pixel
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`line which are formed on the second interlayer insulating
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`film; and a third interlayer insulating film and a common
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`electrode, the common electrode being a black matrix; a
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`second substrate opposed to the first substrate; a liquid
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`crystal layer held between the first and second substrates,
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`and driven by an electric field formed between the pixel
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`electrode and the common electrode, the electric field having
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`a component parallel with the substrates; and a storage
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`capacitor formed by at least parts of the pixel line and the
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`black matrix which parts coextend on the second interlayer
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`insulating film with the third interlayer insulating film
`
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`interposed in between.
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`According to another aspect of the invention, there is
`
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`provided a liquid crystal display device comprising a first
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`substrate comprising a second interlayer insulating film
`
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`made of an organic resin material or an inorganic material;
`
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`a pixel line and a pixel electrode extending from the pixel
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`line which are formed on the second interlayer insulating
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`film; and a third interlayer insulating film, a common
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`electrode, and a capacitance-forming electrode, the common
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`electrode being a black matrix; a liquid crystal layer held
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`Page 13 of 25
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`

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`US 6,771,342 B1
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`3
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`between the first and second substrates, and driven by an
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`electric field formed between the pixel electrode and the
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`common electrode, the electric field having a component
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`parallel with the substrates; and a storage capacitor formed
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`by at least parts of the pixel line and the capacitor-forming
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`electrode which parts coextend on the second interlayer
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`insulating film with the third interlayer insulating film
`
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`interposed in between.
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`The invention can be applied to any of the MIM, passive
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`matrix, active matrix, and like liquid crystal display devices.
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`Further, a dispersion-type liquid crystal display device can
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`be constructed by utilizing the invention. In this case, a
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`second substrate is not necessary.
`The invention has been made in view of the reduction in
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`the widths of electrodes and wiring lines which will proceed
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`in the future. The techniques of the invention are particularly
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`effective in manufacturing a liquid crystal display device
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`that requires microprocessing.
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`According to a further aspect of the invention, there is
`
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`provided a liquid crystal display device comprising an active
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`matrix substrate comprising gate lines and data lines
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`arranged in matrix form on the same active matrix substrate;
`
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`thin-film transistors formed at respective intersections of the
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`gate lines and the data lines; pixel lines connected to the
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`respective thin-film transistors and pixel electrodes extend-
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`ing from the respective pixel lines; and a common electrode
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`at least partially opposed to each of the pixel electrodes, the
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`common electrode being a black matrix; an opposed sub-
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`strate that is opposed to the active matrix substrate; and a
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`liquid crystal layer held between the active matrix substrate
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`and the opposed substrate, and driven by an electric field
`
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`formed between each of the pixel electrodes and the com-
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`mon electrode, the electric field having a component parallel
`with the substrates.
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`
`
`According to another aspect of the invention, there is
`
`
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`
`
`provided a liquid crystal display device comprising an active
`
`
`
`
`
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`
`
`matrix substrate comprising gate lines and data lines
`
`
`
`
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`
`
`arranged in matrix form on the same active matrix substrate;
`
`
`
`
`
`thin-film transistors formed at respective intersections of the
`
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`
`
`
`
`
`gate lines and the data lines; a second interlayer insulating
`
`
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`
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`
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`film and a third interlayer insulating film formed above the
`
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`
`
`thin-film transistors; pixel lines connected to the respective
`
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`
`
`thin-film transistors and pixel electrodes extending from the
`45
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`respective pixel
`lines; and a common electrode at
`least
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`partially opposed to each of the pixel electrodes, the com-
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`mon electrode being a black matrix; an opposed substrate
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`that is opposed to the active matrix substrate; a liquid crystal
`
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`layer held between the active matrix substrate and the
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`opposed substrate, and driven by an electric field formed
`
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`between each of the pixel electrodes and the common
`
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`electrode, the electric field having a component parallel with
`
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`the substrates; and storage capacitors each formed by at least
`
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`parts of the pixel line and the black matrix which parts
`
`
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`
`
`coextend on the second interlayer insulating film with the
`
`
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`
`
`third interlayer insulating film interposed in between.
`
`
`
`
`
`
`
`
`According to another aspect of the invention, there is
`
`
`
`
`
`
`
`provided a liquid crystal display device comprising an active
`
`
`
`
`
`
`
`
`matrix substrate comprising gate lines and data lines
`
`
`
`
`
`
`
`arranged in matrix form on the same active matrix substrate;
`
`
`
`
`
`thin-film transistors formed at respective intersections of the
`
`
`
`
`
`
`
`
`
`gate lines and the data lines; a second interlayer insulating
`
`
`
`
`
`
`
`
`
`film and a third interlayer insulating film formed above the
`
`
`
`
`
`
`
`thin-film transistors; pixel lines connected to the respective
`
`
`
`
`
`
`
`
`thin-film transistors and pixel electrodes extending from the
`
`
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`
`
`
`respective pixel lines; a common electrode at least partially
`
`
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`
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`opposed to each of the pixel electrodes, the common elec-
`
`
`4
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`
`trode being a black matrix; and capacitor-forming electrodes
`
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`
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`formed in a layer different than the pixel lines and the pixel
`
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`
`
`electrodes; an opposed substrate that is opposed to the active
`
`
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`
`
`
`matrix substrate; a liquid crystal layer held between the
`
`
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`
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`
`
`active matrix substrate and the opposed substrate, and driven
`
`
`
`
`
`
`
`
`
`by an electric field formed between each of the pixel
`
`
`
`
`
`
`
`
`electrodes and the common electrode,
`the electric field
`
`
`
`
`
`
`
`
`having a component parallel with the substrates; and storage
`
`
`
`
`
`
`
`
`
`capacitors each formed by at least parts of the pixel line and
`
`
`
`
`
`
`the capacitor-forming electrode which parts coextend on the
`
`
`
`
`
`
`
`
`second interlayer insulating film with the third interlayer
`
`
`
`
`insulating film interposed in between.
`
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`
`In the above configurations, the thin-film transistor which
`
`
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`
`
`controls a voltage applied to the pixel electrode can use, as
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`the active layer, an amorphous silicon film or a crystalline
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`silicon film (polysilicon film).
`
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`Where a pixel area is required to have high response
`
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`speed, where a driver circuit is to be constructed which
`
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`
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`is
`requires high-speed operation, or in similar cases,
`it
`
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`
`
`desirable to employ a thin-film transistor which uses a
`
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`
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`crystalline silicon film as the active layer.
`
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`A thin-film transistor using a crystalline silicon film as the
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`active layer is superior in electrical characteristics to that
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`using an amorphous silicon film. For example, the field-
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`effect mobility is not less than 20 cm2/V.s in the case of an
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`n-channel thin-film transistor and not less than 10 cm2/V.s in
`
`
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`
`
`the case of a p-channel thin-film transistor.
`
`
`
`
`
`
`According to still another aspect of the invention, there is
`
`
`
`
`
`
`provided a manufacturing method of a liquid crystal display
`
`
`
`
`
`
`
`device comprising an active matrix substrate comprising
`
`
`
`
`
`
`
`
`
`gate lines and data lines arranged in matrix form on the same
`
`
`
`
`
`
`active matrix substrate;
`thin-film transistors formed at
`
`
`
`
`
`
`
`
`
`respective intersections of the gate lines and the data lines,
`
`
`
`
`
`
`
`
`and each having, as an active layer, a crystalline silicon film;
`
`
`
`
`
`
`
`
`
`a second interlayer insulating film formed above the thin-
`
`
`
`
`
`
`
`film transistors; pixel
`lines connected to the respective
`
`
`
`
`
`
`
`
`thin-film transistors and pixel electrodes extending from the
`
`
`
`
`
`
`
`
`respective pixel
`lines; and a common electrode at
`least
`
`
`
`
`
`
`partially opposed to each of the pixel electrodes; an opposed
`
`
`
`
`
`
`
`
`substrate that is opposed to the active matrix substrate; and
`
`
`
`
`
`
`
`
`
`
`a liquid crystal layer held between the active matrix sub-
`
`
`
`
`
`
`
`
`strate and the opposed substrate, and driven by an electric
`
`
`
`
`
`
`
`
`
`field formed between each of the pixel electrodes and the
`
`
`
`
`
`
`
`common electrode, the electric field having a component
`
`
`
`
`
`
`
`
`parallel with the active matrix substrate, said manufacturing
`
`
`
`
`
`
`
`method comprising the steps of forming a second interlayer
`
`
`
`
`
`
`
`insulating film made of an organic resin material and/or an
`
`
`
`
`
`
`
`
`
`
`inorganic material so as to cover data lines and a first
`
`
`
`
`
`
`
`
`interlayer insulating film that covers gate lines; forming a
`
`
`
`
`
`
`
`black matrix on the second interlayer insulating film; form-
`
`
`
`
`
`
`
`
`ing a third interlayer insulating film so as to cover the black
`
`
`
`
`
`
`
`
`
`matrix; forming contact holes through the second and third
`
`
`
`
`
`
`
`
`interlayer insulating films; and forming, on the third inter-
`
`
`
`
`
`
`
`
`
`layer insulating film, pixel lines and pixel electrodes extend-
`
`
`
`
`
`
`
`
`
`ing from the respective pixel lines, wherein each of storage
`
`
`
`
`
`
`
`
`capacitors is formed by at least parts of the pixel line and the
`
`
`
`
`
`
`
`
`black matrix which parts coextend on the second interlayer
`
`
`
`
`
`
`
`
`insulating film with the third interlayer insulating film
`
`
`interposed in between.
`
`
`
`
`
`
`
`
`According to another aspect of the invention, there is
`
`
`
`
`
`
`provided a manufacturing method of a liquid crystal display
`
`
`
`
`
`
`
`device comprising an active matrix substrate comprising
`
`
`
`
`
`
`
`
`
`gate lines and data lines arranged in matrix form on the same
`
`
`
`
`
`
`active matrix substrate;
`thin-film transistors formed at
`
`
`
`
`
`
`
`
`
`respective intersections of the gate lines and the data lines,
`
`
`
`
`
`
`
`
`and each having, as an active layer, a crystalline silicon film;
`
`
`
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`
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`5
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`10
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`15
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`20
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`25
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`30
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`35
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`40
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`50
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`55
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`60
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`65
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`Page 14 of 25
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`Page 14 of 25
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`

`

`
`
`US 6,771,342 B1
`
`
`5
`
`
`
`
`
`
`
`
`
`a second interlayer insulating film formed above the thin-
`
`
`
`
`
`
`
`film transistors; pixel
`lines connected to the respective
`
`
`
`
`
`
`
`
`thin-film transistors and pixel electrodes extending from the
`
`
`
`
`
`
`
`
`respective pixel
`lines; and a common electrode at
`least
`
`
`
`
`
`
`
`partially opposed to each of the pixel electrodes; an opposed
`
`
`
`
`
`
`
`
`substrate that is opposed to the active matrix substrate; and
`
`
`
`
`
`
`
`
`
`
`a liquid crystal layer held between the active, matrix sub-
`
`
`
`
`
`
`
`
`strate and the opposed substrate, and driven by an electric
`
`
`
`
`
`
`
`
`
`field formed between each of the pixel electrodes and the
`
`
`
`
`
`
`
`common electrode, the electric field having a component
`
`
`
`
`
`
`
`
`parallel with the active matrix substrate, said manufacturing
`
`
`
`
`
`
`
`method comprising the steps of forming a second interlayer
`
`
`
`
`
`
`
`insulating film made of an organic resin material and/or an
`
`
`
`
`
`
`
`
`inorganic material so as to cover the data lines and a first
`
`
`
`
`
`
`
`
`
`interlayer insulating film that covers the gate lines; forming
`
`
`
`
`
`
`
`
`contact holes through the second interlayer insulating film;
`
`
`
`
`
`
`
`
`forming, on the second interlayer insulating film, pixel lines
`
`
`
`
`
`
`
`
`and pixel electrodes extending from the respective pixel
`
`
`
`
`
`
`
`lines; forming a third interlayer insulating film so as to cover
`
`
`
`
`
`
`
`
`
`
`the pixel lines and the pixel electrodes; and forming a black
`
`
`
`
`
`
`
`
`matrix on the third interlayer insulating film, wherein each
`
`
`
`
`
`
`
`
`of storage capacitors is formed by at least parts of the pixel
`
`
`
`
`
`
`
`
`line and the black matrix which parts coextend on the second
`
`
`
`
`
`
`
`
`interlayer insulating fill with the third interlayer insulating
`
`
`
`film interposed in between.
`
`
`
`
`
`
`
`
`
`One of the main points of the technical means of the
`invention resides in the commonization of a black matrix
`
`
`
`
`
`
`
`
`
`
`
`
`and common electrodes. It is intended to realize a configu-
`ration in which a lateral electric field is formed between the
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`black matrix (having substantially the same function as the
`
`
`
`
`
`
`
`
`common electrodes) and a pixel electrode that extends from
`
`
`
`a pixel line.
`
`
`
`
`
`
`
`Further, in a liquid crystal display device having such a
`
`
`
`
`
`
`parallel electrode structure, a storage capacitor is formed by
`
`
`
`
`
`
`
`
`the black matrix and a pixel line that is connected to a
`thin-film transistor.
`
`
`
`
`
`
`
`
`
`
`
`The idea of commonizing the black matrix and the
`
`
`
`
`
`
`common electrodes, which are considered separate members
`
`
`
`
`
`
`
`
`conventionally, is entirely new, and the formation of the
`
`
`
`
`
`
`
`
`
`
`storage capacitor by the black matrix and the pixel line is
`
`
`
`
`
`
`
`
`entirely different from the technique disclosed in the above-
`
`
`
`
`
`mentioned publication No. Hei. 7-36058.
`
`
`
`
`
`
`
`
`45
`Another important feature of the invention is that a
`
`
`
`
`
`
`
`manufacturing process can be simplified greatly by com-
`
`
`
`
`
`
`
`
`monizing the black matrix and the common electrodes.
`
`
`
`
`
`
`
`
`
`
`FIGS. 1A and 1B are top views of a pixel region,
`
`
`
`
`
`
`
`according to the invention, of a liquid crystal display device.
`
`
`
`
`
`
`
`
`
`
`In FIG. 1A, reference numerals 101 and 102 denote a gate
`
`
`
`
`
`
`
`
`
`line for transmitting a gate signal and a data line for
`
`
`
`
`
`
`
`
`transmitting an image signal, respectively. (In FIG. 1A, the
`
`
`
`
`
`
`
`
`
`
`
`gate lines 101 and the data lines 102 are shown by broken
`
`
`
`
`
`
`
`lines because they exist under a black matrix.)
`
`
`
`
`
`
`
`
`
`
`The gate lines 101 and the data lines 102 are arranged in
`
`
`
`
`
`
`
`
`matrix form on the same substrate, and thin-film transistors
`
`
`
`
`
`
`
`
`are disposed for each intersection of those lines. Reference
`
`
`
`
`
`
`
`numeral 103 denotes a semiconductor layer that constitutes
`
`
`
`
`
`
`
`
`the active layer of the thin-film transistor. Ablack matrix 104
`
`
`
`
`
`
`
`
`(hatched in FIGS. 1A and 1B) are formed above the gate
`
`
`
`
`
`
`
`
`
`
`lines 101, the data lines 102, and the semiconductor layer
`103 so as to cover those members.
`
`
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`The data lines 102 and the black matrix 104 are insulated
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`from each other by a second interlayer insulating film of
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`0.1—5.0 pm in thickness. The second interlayer insulating
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`film is made of an organic or inorganic material.
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`6
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`line 105 and a pixel electrode 106
`Further, a pixel
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`extending therefrom are formed !above the black matrix 104
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`through a third interlayer insulating film. FIG. 1B shows a
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`state that the pixel line 105 and the pixel electrode 106 are
`laid on the structure of FIG. 1A.
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`Although the pixel line 105 and the pixel electrode 106
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`constitute an integral part in FIG. 1B, the present inventors
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`clearly distinguish between those members based on their
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`functions. That is, the pixel electrode 106 is defined as the
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`portion extending from the pixel line 105 to the pixel region
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`(i.e., the opening of the black matrix 104).
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`That is, the pixel line 105 and the pixel electrode 106 are
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`considered entirely different from each other because the
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`pixel line 105 is provided to form a storage capacitor with
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`the black matrix 104 whereas the pixel electrode 106 is
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`provided to form a lateral electric field between itself and the
`black matrix 104.
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`In the above structure, a storage capacitor is formed by the
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`black matrix 104 and the pixel line 105 with the third
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`interlayer insulating film interposed in between in the region
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`where the black matrix 104 and the pixel line 105 overlap
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`with each other. The third interlayer insulating film needs to
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`be constituted of an insulating film having a larger relative
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`dielectric constant than the second interlayer insulating film.
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`Although as shown in FIG. 1B a storage capacitor is
`formed in the same manner as in the above case in small
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`regions where the pixel electrode 106 exists over the black
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`matrix 104, it can substantially be disregarded in the case of
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`improving the open area ratio (aperture ratio) by reducing
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`the electrode width, which is one of the main points of, the
`invention.
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`Lateral electric fields (indicated by arrows in FIG. 1B) for
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`driving the liquid crystal are formed between the pixel
`electrode 106 and the black matrix 104.
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`BRIEF DESCRIPTION OF THE DRAWINGS
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`FIGS. 1A and 1B are top views showing the structure of
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`a pixel region of a liquid crystal display device according to
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`a first embodiment of the invention;
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`FIGS. 2A—2D, 3A—3B, and FIG. 4 are sectional views
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`showing a manufacturing process of the pixel region of a
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`liquid crystal display device according to the first embodi-
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`FIGS. 5A and 5B are sectional views showing the struc-
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`ture of a pixel region of a liquid crystal display device
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`according to a fourth embodiment of the invention;
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`FIG. 6 is a top view showing a pixel region of a liquid
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`crystal display device according to a fifth embodiment of the
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`invention;
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`FIG. 7 is a top view showing a pixel region of a liquid
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`crystal display device according to a sixth embodiment of
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`the i