Abstract:
A liquid crystal display device with enhanced brightness through improving a partial structure for applying potential to a pixel electrode is provided. The liquid crystal display device includes: a pixel electrode with a plurality of openings; an opposite electrode disposed to face the pixel electrode with an insulating layer in between; a liquid crystal layer disposed on an opposite side of the pixel electrode from the opposite electrode; a selection line utilized to select a pixel; a thin film transistor disposed on the opposite side of the opposite electrode from the pixel electrode as to drive the pixel and utilizing a part of the selection line as a gate thereof; and an interlayer conductor connecting between the thin film transistor and the pixel electrode. The opposite electrode has an opposite electrode hole which allows the interlayer conductor to pass therethrough, and the opposite electrode hole partly overlaps the selection line.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention relates to a liquid crystal display device in which displaying is performed by a liquid crystal in an in-plane switching mode. 
         [0003]    2. Description of the Related Art 
         [0004]    There is a liquid crystal display device having a liquid crystal structure of an in-plane switching mode such as an FFS (Fringe Field Switching) mode. The liquid crystal display device in the FFS mode has an opposite electrode. A pixel electrode having a slit-shaped opening is disposed to oppose the opposite electrode through an insulating layer. Further, a liquid crystal layer is disposed above the pixel electrode. A conductive contact is disposed to penetrate the insulating layer in the layer stack direction, and the pixel electrode and a TFT (Thin Film Transistor) for driving the pixel electrode are made conductive via the conductive contact. In such a liquid crystal display device, when voltage is applied from a data line connected to the TFT to the pixel electrode, an electric field is generated from the pixel electrode toward the opposite electrode below the pixel electrode via the liquid crystal layer and the slit, and thereby, a transverse electric field is applied to the liquid crystal layer to perform driving. Japanese Unexamined Patent Application Publication No. 2008-64947 discloses a liquid crystal display device in the FFS mode. 
       SUMMARY OF THE INVENTION 
       [0005]    Since the liquid crystal display device is requested to improve brightness in recent years, an attempt to increase the aperture ratio is being made. To increase the aperture ratio, it is necessary to enlarge the area of the light transmission region as much as possible. As described above, since the conductive contact is necessary to connect the pixel electrode and the TFT and the space for disposing the conductive contact is necessary, a sufficiently high aperture ratio is not necessarily obtained. There is, however, no proposal for improvement in this regard. 
         [0006]    It is therefore desirable to provide a liquid crystal display device capable of increasing brightness by improving a structure for applying drive voltage to a pixel electrode. 
         [0007]    A liquid crystal display device according to an embodiment of the present invention includes: a pixel electrode with a plurality of openings; an opposite electrode disposed so as to face the pixel electrode with an insulating layer in between; a liquid crystal layer disposed on an opposite side of the pixel electrode from the opposite electrode; a selection line utilized to select a pixel; a thin film transistor disposed on the opposite side of the opposite electrode from the pixel electrode so as to drive the pixel, and utilizing a part of the selection line as a gate thereof; and an interlayer conductor electrically connecting between the thin film transistor and the pixel electrode. The opposite electrode has an opposite electrode hole which allows the interlayer conductor to pass therethrough, and the opposite electrode hole partly overlaps the selection line. 
         [0008]    In the liquid crystal display device according to the embodiment of the invention, incident light from a backlight passes through the pixel electrode and the opposite electrode and enters the liquid crystal layer and, on the other hand, is blocked by the selection line and the interlayer conductor. When the thin film transistor is turned on by a signal supplied from the selection line and image signal voltage is applied to the pixel electrode, an electric field is generated from the pixel electrode toward the opposite electrode below the pixel electrode via the liquid crystal layer and the opening in the pixel electrode. Thereby, a transverse electric field is applied to the liquid crystal layer, liquid crystal molecules in the liquid crystal layer selectively turn, and light passing through the liquid crystal layer is modulated. Since the opposite electrode hole which allows the interlayer conductor to pass therethrough is provided in a position overlapping the selection line, as a result, the interlayer conductor which blocks incident light is positioned extremely close to the selection line. Therefore, the opening region in the pixel electrode may be enlarged to a position closer to the selection line as compared with that in the conventional technique. Moreover, since a part of the selection line is used as the gate of the thin film transistor, as compared with the case of leading a gate part separately from a selection line to configure a thin film transistor, a light shield region generated by the space for disposing the thin film transistor is accordingly reduced, and the opening region in the pixel electrode is enlarged by an amount of the reduction. 
         [0009]    In the liquid crystal display device according to an embodiment of the invention, preferably, the interlayer conductor has a first extending portion which extends along a plane of a layer between the opposite electrode and the selection line so as to cover an overlap region where the opposite electrode hole partly overlaps the selection line. In this case, a leak electric field from the selection line to the liquid crystal layer via the opposite electrode hole is blocked by a part of the interlayer conductor extending along the layer stack plane, and disturbance of the electric field is suppressed. Preferably, the interlayer conductor further has a second extending portion different from the first extending portion, a first inner edge region of the opposite electrode, which is a part of a whole inner edge region surrounding the opposite electrode hole, faces the overlap region, and a second inner edge region of the opposite electrode, which is different from the first inner edge region, overlaps the second extending portion of the interlayer conductor or the pixel electrode, or overlaps both of the second extending portion of the interlayer conductor and the pixel electrode. In the case where the second inner edge region of the opposite electrode is covered with the pixel electrode, disturbance of the electric field which may occur when the second inner edge region is not covered with the pixel electrode is suppressed. Alternatively, in the case where the part of the interlayer conductor overlaps the second inner edge region, a part where no opposite electrode exists (liquid crystal controllability is low) is covered with the part of the interlayer conductor. Accordingly, even if the electric field generated between the pixel electrode and the opposite electrode is disturbed, a part of the interlayer insulating film blocks light. As a result, the part of low liquid crystal controllability is prevented from contributing to display. Therefore, drop in the contrast is prevented. 
         [0010]    In the liquid crystal display device according to the embodiment of the present invention, since the opposite electrode hole which allows the interlayer conductor to pass therethrough is located in a position so as to overlap the selection line, the area of the transmission region may be enlarged, and display brightness improves. In addition, since the opening in the pixel electrode may be enlarged to a position closer to the selection line as compared with the conventional technique, the opening area is increased, and display contrast improves. Moreover, by utilizing a part of the selection line as a gate part of the thin film transistor, the space for disposing the thin film transistor is reduced, so that the area of the light transmission region may be further enlarged by the amount of the reduced space, and the opening in the pixel electrode may be enlarged, thereby, in this regard as well, contributing to improvement of the display brightness and display contrast. 
         [0011]    Other and further objects, features and advantages of the invention will appear more fully from the following description. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0012]      FIG. 1  is a partly-enlarged plan view of a liquid crystal display device according to a first embodiment. 
           [0013]      FIG. 2  is an enlarged plan view of a portion of a first contact in the liquid crystal display device illustrated in  FIG. 1 . 
           [0014]      FIG. 3  is a diagram illustrating the positional relationship in the plane direction of main parts around the area where the first contact of the liquid crystal display device is provided. 
           [0015]      FIG. 4  is a cross section taken along line A-A of  FIG. 2 . 
           [0016]      FIGS. 5A and 5B  are perspective views each illustrating a schematic configuration of the liquid crystal display device. 
           [0017]      FIGS. 6A and 6B  are cross sections of an opposite electrode, a pixel electrode, and a liquid crystal layer for explaining operation of the liquid crystal display device. 
           [0018]      FIG. 7  is a cross section of a liquid crystal display device according to a second modification. 
           [0019]      FIG. 8  is a cross section of a liquid crystal display device according to a third modification. 
           [0020]      FIG. 9  is an enlarged plan view of a portion of a contact in the liquid crystal display device according to a second embodiment. 
           [0021]      FIG. 10  is an enlarged plan view of a portion of a contact in the liquid crystal display device according to a third embodiment. 
           [0022]      FIG. 11  is a partly-enlarged plan view of a liquid crystal display device according to a comparative example. 
           [0023]      FIG. 12  is an enlarged plan view of a portion of a contact in the liquid crystal display device illustrated in  FIG. 11 . 
           [0024]      FIG. 13  is a cross section taken along line C-C of  FIG. 12 . 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0025]    Embodiments of the present invention will be described in detail hereinbelow with reference to the drawings. 
       First Embodiment 
       [0026]      FIG. 1  is a plan view illustrating the configuration of a main part of a liquid crystal display device according to a first embodiment of the present invention.  FIGS. 2 and 3  are enlarged views of a part (a part around a contact) in the liquid crystal display device illustrated in  FIG. 1 . In  FIG. 3 , a part of the components (such as a pixel electrode) is not illustrated.  FIG. 4  illustrates a sectional structure taken along line A-A of  FIG. 2 . 
         [0027]    As illustrated in  FIG. 4 , a liquid crystal display device  1  is provided with a glass substrate  10 . On the top face of the glass substrate  10 , a plurality of gate lines  11  as selection lines extend in the row direction (the direction perpendicular to the drawing surface). In a region of one pixel, the gate line  11  serves as a gate  12   a  of a switching element for driving the pixel, i.e., a thin film transistor (TFT)  12 . On the top face of the glass substrate  10 , a gate insulating film  13  is provided, and the gate lines  11  are covered with the gate insulating film  13 . 
         [0028]    On the top face of the gate insulating film  13 , a semiconductor layer  14  is provided. In the present embodiment, the semiconductor layer  14  has a substantially U-shape in plan view as illustrated in  FIG. 1 . One of arm parts of the U shape crosses the gate line  11 . The region of the semiconductor layer  14 , where the gate line  11  and the semiconductor layer  14  cross each other, serves a channel  12   b  of the TFT  12 . The gate  12   a , the gate insulating film  13 , and the channel  12   b  of the semiconductor layer  14  configure a main part of the TFT  12 . 
         [0029]    A first contact  15  (which will be described later) as an interlayer conductor is provided in one end (source) of the U shape of the semiconductor layer  14 , and a second contact  17  is provided in the other end (drain). The first contact  15  is provided to connect the source of the semiconductor layer  14  and a pixel electrode  25 , which will be described later, in the layer stack direction. The second contact  17  is provided to connect a data line  16  extending in the column direction and the drain of the semiconductor layer  14  in the layer stack direction. A data signal (pixel voltage) is supplied from the data line  16  to the semiconductor layer  14  via the second contact  17 . The data signal further passes between the source and drain of the TFT  12  and supplied from the semiconductor layer  14  (drain) to the pixel electrode  25  via the first contact  15 . 
         [0030]    Over the semiconductor layer  14  and the gate insulating film  13 , a transistor protection film  18  having insulating property is provided so as to cover the semiconductor layer  14  and the gate insulating film  13  ( FIG. 4 ). In the transistor protection film  18 , a contact hole  15   h  is provided in a position adjacent to the gate line  11  and is filled with a conductor, thereby configuring the first contact  15 . The first contact  15  has a part (extension part, or a first extending portion)  15   a  extending in the direction toward the gate line  11  along the top face of the transistor protection film  18 , a part (penetration part)  15   b  penetrating the transistor protection film  18  in the layer stack direction, and an extension part  15   c  (a second extending portion) extending in three directions other than the extension direction of the extension part  15   a . The front end part of the extension part  15   a  extends to a position overlapping the gate line  11 . 
         [0031]    On the transistor protection film  18  and the first contact  15 , an interlayer insulating film  19  is provided so as to cover the transistor protection film  18  and the first contact  15 . In the interlayer insulating film  19 , an interlayer insulating film hole  20  reaching the top face of the first contact  15  is formed in the position where the first contact  15  is formed. 
         [0032]    An opposite electrode  21  is formed on the top face of the interlayer insulating film  19 . In the opposite electrode  21 , an opposite electrode hole  22  having a rectangular shape is formed. The opposite electrode hole  22  is formed so as to include the interlayer insulating film hole  20  and to be larger than the interlayer insulating film hole  20  in the plane direction. As a result, the interlayer insulating film hole  20  is positioned in the region on the inside of the opposite electrode hole  22 . The opposite electrode hole  22  is formed above the gate line  11  so as to overlap the gate line  11 . That is, a part (inner edge region  27 ) of an inner edge region surrounding the opposite electrode hole  22  is terminated above the gate line  11 . An overlap region  101  where the gate line  11  and the opposite electrode hole  22  overlap is covered with the extension part  15   a  of the first contact  15 . In other words, the front end part of the extension part  15   a  of the first contact  15  extends to a portion passing the position of an inner edge  21   a  of the opposite electrode hole  22  between the opposite electrode  21  and the gate line  11  to be terminated at the portion. Similarly, a region  28  other than the inner edge region  27  in the inner edge region surrounding the opposite electrode hole  22  also overlaps the other extension part  15   c  of the first contact  15  above the first contact  15 . In other words, the front end part of the other extension part  15   c  of the first contact  15  extends to a portion passing the position of an inner edge  21   b  other than the part overlapping the semiconductor layer  14 , of the inner edge  21   a  of the opposite electrode hole  22  to be terminated at the portion. 
         [0033]    The interlayer insulating film  19 , the opposite electrode  21 , and the interlayer insulating film hole  20  are covered with a pixel insulating film  23  (insulating layer). In the pixel insulating film  23 , a pixel insulating film hole  24  penetrating the inside of the opposite electrode hole  22  in the opposite electrode  21  and the interlayer insulating film hole  20  in the interlayer insulating film  19  in the layer stack direction and reaching the top face of the first contact  15  is formed. 
         [0034]    On the pixel insulating film  23 , the pixel electrodes  25  are formed on the pixel unit basis. As illustrated in  FIG. 1 , the pixel electrode  25  is disposed across two neighboring gate lines  11  so as to overlap the gate lines. As illustrated in  FIGS. 1 and 4 , the pixel electrode  25  covers the inner face of the pixel insulating film hole  24  (the inner wall face and the top face of the first contact  15 ), so that the drain of the semiconductor layer  14  and the pixel electrode  25  are electrically connected to each other via the first contact  15 . The pixel electrode  25  is formed in a position and a size so as to completely cover the opposite electrode hole  22 . In the pixel electrode  25 , a plurality of elongated openings (slits  26 ) are formed along a direction parallel to the data line  16 . The slits  26  (three slits  26  in  FIG. 1 ) positioned in a center portion of the slits  26  extend close to the TFT  12 , that is, close to the first contact  15 , and the slits  26  (two slits in  FIG. 1 ) in the peripheral parts extend very close to the gate lines. A cross section taken along line B-B of  FIG. 1  is as illustrated in  FIG. 6  which will be described later. 
         [0035]      FIGS. 5A and 5B  schematically illustrate a perspective structure of the liquid crystal display device. As illustrated in  FIGS. 5A and 5B , on the top face side (light outgoing side) of the pixel electrode  25 , a first alignment film  30 , a liquid crystal layer  31 , a second alignment film  32 , and a second polarizer  34  are disposed. On the under face side (light incident side) of the glass substrate  10  (opposite electrode  21 ), a first polarizer  33  is disposed. 
         [0036]    The liquid crystal display device  1  having such a configuration is manufactured, for example, as follows. First, as a switching element for driving pixels of the liquid crystal display device  1 , the TFT  12  is formed. To form the TFT  12 , first, a metal film serving as the gate  12   a  (the gate line  11 ) of the TFT  12  is formed on the glass substrate  10 . The metal film may be formed by depositing a metal material such as molybdenum by using, for example, sputtering or the like. After that, a mask is formed on the top face of the metal film by using the photolithography technique, the metal film exposed from an opening in the mask is etched and, after that, the mask is removed. In such a manner, the gate  12   a  of the TFT  12  also serving as the gate line  11  is formed. 
         [0037]    Next, the gate insulating film  13  covering the glass substrate  10  and the gate line  11  is formed. The gate insulating film  13  may be formed by depositing an insulating material such as silicon nitride on the top face of the glass substrate  10  by using a film forming method such as chemical vapor deposition (CVD). 
         [0038]    Next, the semiconductor layer  14  is formed. To form the semiconductor layer  14 , first, a semiconductor material such as amorphous silicon which will become the semiconductor layer  14  is deposited on the top face of the gate insulating film  13  by using a film forming method such as CVD. After that, to obtain the semiconductor layer  14  having the shape illustrated in  FIG. 1 , a mask is formed on the top face of the semiconductor material by using the photolithography technique, the semiconductor material exposed from an opening in the mask is etched and, after that, the mask is removed. As a result, the semiconductor layer  14  having one end to which the first contact  15  is connected, the other end to which the second contact  17  is connected, and the part serving as the channel  12   b  of the TFT  12  is formed. 
         [0039]    Next, the transistor protection film  18  protecting the TFT  12  is formed on the top face of the semiconductor layer  14  and the gate insulating film  13 . To form the transistor protection film  18 , first, using a film forming method such as CVD, an insulating material such as silicon nitride is deposited on the top face of the gate insulating film  13  to cover the semiconductor layer  14 . After that, a mask is formed on the top face of the gate insulating film  13  by using the photolithography technique so that the first contact  15  and the second contact  17  are disposed in the layer stack direction. Then, the insulating material exposed from the opening in the mask is etched and, after that, the mask is removed. As a result, the transistor protection film  18  is formed, and the transistor protection film  18  is configured to have the first contact hole  15   h  in which the penetration part  15   b  of the first contact  15  is disposed and a second contact hole in which the second contact  17  is disposed. 
         [0040]    Next, a transistor contact metal film which becomes the first contact  15  and the data line  16  is formed on the top face of the transistor protection film  18 . To form the transistor contact metal film, first, by using a film forming method such as sputtering, for example, three layers of titanium, aluminum, and titanium are stacked on the top face of the transistor protection film  18 . After that, a mask is formed on the top face of the transistor contact metal film by using the photolithography technique. Then, parts which are not covered with the mask are etched, and the mask is removed. As a result, the first contact  15  including the part extending in the plane direction, i.e., including the part in which an end of the transistor contact metal film in the inner edge region overlaps the gate line  11  in plan view, and the data line  16  extending in the column direction, are formed. Therefore, the first contact  15  is disposed in a layer between the opposite electrode  21  and the gate line  11 . 
         [0041]    Next, the interlayer insulating film  19  is formed on the top face of the transistor protection film  18 , the first contact  15 , and the data line  16 . The interlayer insulating film  19  can be made of an insulating material such as acrylic resin. In this case, if the acrylic resin is photosensitive, the interlayer insulating film hole  20  is easily formed by using the photolithography technique. Thereby, the interlayer insulating film  19  bringing insulation between the first contact  15  and the data line  16  and the opposite electrode  21 , and from which a part of the first contact  15  is exposed via the interlayer insulating film hole  20  is obtained. 
         [0042]    Next, the opposite electrode  21  as a transparent electrode is formed on the top face of the interlayer insulating film  19 . To form the opposite electrode  21 , first, by using a film forming method such as sputtering, for example, an electrode material such as indium oxide is formed on the top face of the interlayer insulating film  19 . After that, to form the opposite electrode hole  22 , a mask is formed on the top face of the opposite electrode  21  by using the photolithography technique. Then, the electrode material exposed from an opening in the mask is etched and, after that, the mask is removed. As a result, the opposite electrode  21  having the opposite electrode hole  22  is formed. As illustrated in  FIG. 4 , the opposite electrode hole  22  of the present embodiment is formed to be larger than the interlayer insulating film hole  20  and to be smaller than the part extending in the plane direction of the first contact  15 . Therefore, the inner edge region of the inner edge  21   a  forming the opposite electrode hole  22  overlaps both of the first contact  15  and the gate line  11  in plan view. 
         [0043]    Next, to apply the electric field to the liquid crystal layer  31 , the pixel insulating film  23  is formed on the top face of the opposite electrode  21 . The pixel insulating film  23  is formed by depositing, for example, a dielectric such as silicon nitride on the top face of the opposite electrode  21  using a film deposition method such as CVD. Then, a mask is formed on the top face of the dielectric layer by using the photolithography technique. Thereafter, a part which is not covered with the mask is etched, and the mask is removed. Thereby, the pixel insulating film  23  having the pixel insulating film hole  24  is formed, and the pixel insulating film hole  24  of the present embodiment is disposed on the inside of the interlayer insulating film hole  20  and the opposite electrode hole  22 . 
         [0044]    Next, the pixel electrode  25  which applies the potential for driving the liquid crystal is formed on the top face of the pixel insulating film  23 . The pixel electrode  25  may be formed by depositing, for example, an electrode material such as indium oxide using a film depositing method such as sputtering and, after that, forming a pattern covering the slit  26  and the opposite electrode hole  22  in plan view, so that the electric field is applied across the pixel electrode  25  and the opposite electrode  21  via the pixel insulating film  23 , by using a mask obtained by the photolithography technique and etching. 
         [0045]    After that, the first alignment film  30 , the liquid crystal layer  31 , the second alignment film  32 , and the second polarizer  34  are disposed on the top face side of the pixel electrode  25 , and the first polarizer  33  is disposed on the under face side of the glass substrate  10 , thereby obtaining the liquid crystal display device  1 . 
         [0046]    Next, the operation of the liquid crystal display device  1  of the present embodiment will be described. First, referring to  FIGS. 5A and 5B  and  FIGS. 6A and 6B , basic operation will be described.  FIGS. 5A and 5B  illustrate the perspective configuration of the liquid crystal display device  1 .  FIGS. 6A and 6B  illustrate a cross section (taken along line B-B of  FIG. 1 ) of the liquid crystal display device  1 .  FIGS. 5A and 6A  illustrate a state in which no voltage is applied, and  FIGS. 5B and 6B  illustrate a state in which the voltage is applied. 
         [0047]    Light is incident (arrows C and D in  FIG. 4 ) on the liquid crystal display device  1  from the rear side (down side in  FIG. 1 ) of the glass substrate  10 . The incident light D is blocked by portions made of metal such as the gate line  11 , the first contact  15 , the second contact  17 , the data line  16 , and the like, and passes through the other parts and enters the liquid crystal layer  31  (incident light C). 
         [0048]    The light incident on the liquid crystal layer  31  is subject to space modulation in an FFS mode as described below when the light passes through the liquid crystal layer  31 . 
         [0049]    As illustrated in  FIGS. 5A and 6A , in a state where no voltage is applied across the opposite electrode  21  and the pixel electrode  25 , the axis of a liquid crystal molecule  35  as a component of the liquid crystal layer  31  is orthogonal to the transmission axis of the first polarizer  33  on the incidence side, and is parallel with the transmission axis of the second polarizer  34  on the outgoing side. Consequently, the incident light “h” having passed through the first polarizer  33  on the incident side reaches the second polarizer  34  on the outgoing side without causing a phase difference in the liquid crystal layer  31  and is absorbed, so that black display is resulted. 
         [0050]    On the other hand, as illustrated in  FIGS. 5B and 6B , in a state where voltage is applied across the opposite electrode  21  and the pixel electrode  25 , the alignment direction of the liquid crystal molecules  35  is turned obliquely to the extension direction of the pixel electrode  25  by the electric field E generated between the pixel electrodes  25 . At this time, the electric field intensity in the white display mode is optimized so that the liquid crystal molecule  35  positioned in the center in the thickness direction of the liquid crystal layer  31  turns at about 45 degrees. Thereby, a phase difference occurs in the incident light having passed through the first polarizer  33  on the incident side while passing through the liquid crystal layer  31 . Thus, the light becomes linearly polarized light which is turned at 90 degrees and passes through the second polarizer  34  on the outgoing side, so that white display is resulted. 
         [0051]    The action unique to the liquid crystal display device  1  of the present embodiment will now be described. First, a comparative example will be described for comparison. 
         [0052]      FIG. 11  is a plan view illustrating the configuration of a main part of a liquid crystal display device  100  according to a comparative example.  FIG. 12  is an enlarged view of a part (a portion around a contact) in the liquid crystal display device  100 .  FIG. 13  is a cross section taken along line C-C of  FIG. 12 . 
         [0053]    As in the liquid crystal display device  1  of the present embodiment, the liquid crystal display device  100  has gate lines  111  disposed in the row direction and data lines  116  disposed in the column direction. A gate  112   a  of a TFT  112  is configured by two metal films extending in the column direction, and one end of each of the metal films is connected to the gate line  111 . A semiconductor layer  114  is disposed above the gate  112   a  via a gate insulating film  113  and extends along the gate lines  111 . A part facing the gate  112   a , of the semiconductor layer  114  serves as a channel  112   b  of the TFT  112 . On the top face of the semiconductor layer  114 , a transistor protection film  118  is provided. The transistor protection film  118  is provided with a first contact  115  penetrating the film  118  in the layer stack direction and reaching the top face of one end side of the semiconductor layer  114 . The other end side of the semiconductor layer  114  is connected to the data line  116  via a second contact  117  ( FIG. 11 ). 
         [0054]    Above the transistor protection film  118  and the like, an interlayer insulating film  119 , an opposite electrode  121 , a pixel insulating film  123 , and a pixel electrode  125  are provided. In the interlayer insulating film  119 , an interlayer insulating film hole  120  reaching the top face of the first contact  115  is provided. The opposite electrode  121  is provided on the interlayer insulating film  119  and has an opposite electrode hole  112 . The pixel insulating film  123  is provided so as to cover the opposite electrode  121  and the interlayer insulating film  119 . In the pixel insulating film  123 , a pixel electrode hole  124  reaching the top face of the first contact  115  is formed. On the pixel insulating film  123 , the pixel electrode  125  in which a plurality of openings (slits) are formed is formed. The pixel electrode  125  is connected to the first contact  115  via the pixel electrode hole  124 . 
         [0055]    The gate  112   a  of the TFT  112 , the first contact  115  making the pixell electrode  125  and the semiconductor layer  114  conductive and the like, are light shield regions which are made of a metal and do not transmit incident light, and are parts which do not contribute to display of the liquid crystal display device  100 . Therefore, in the comparative example, the area of the light shield regions is relatively large for the following reasons.
   (1) The first contact  115  is formed in a position completely apart from the gate line  111 , and the sum of the light shield area of the first contact  115  and that of the gate line  111  is large.   (2) Since the gate  112   a  is led from the gate line  111  and used as the gate of the TFT  112 , the light shield area of the gate  112   a  is added to the light shield area of the gate line  111 .   
 
         [0058]    In contact, in the liquid crystal display device  1  of the present embodiment, the region of the first contact  15  is located close to a periphery in the pixel region so that the first contact  15  overlaps with the gate line  11 . Specifically, the opposite electrode hole  22  is formed above the gate line  11  in a position so that the opposite electrode hole  22  is overlapped with the gate line  11 . As a result, the first contact  15  itself is formed in a position sufficiently close to the gate line  11 , and the sum between the light shield area of the first contact  15  and the light shield area of the gate line  11  is further decreased. 
         [0059]    In addition, in the liquid crystal display device  1  of the present embodiment, the gate  12   a  of the TFT  12  also serves as the gate line  11  (that is, a part of the gate line  11  is used as the gate of the TFT  12 ). In this point as well, the area of the light shield region is made smaller than that in the comparative example. 
         [0060]    Consequently, the light shield amount is reduced as a whole and the light transmission amount is increased, so that display brightness improves. 
         [0061]    As described above, as a result of forming the formation region of the first contact  15  close to the periphery in the pixel region so that the first contact  15  partly overlaps the gate line  11 , the slit  26  in the pixel electrode  25  may be enlarged to a position closer to the gate line  11  more than the comparative case by an amount that the formation region is brought close to the overlapping part. Moreover, a part (gate  12   a ) of the gate line  11  is used as the gate portion of the TFT  12 , so that the space in which the TFT  12  is disposed may be reduced as compared with the comparative example, and the slit  26  in the pixel electrode  25  may be enlarged by the reduction amount. Specifically, a hatched region X 1  in  FIG. 2  is a slit region enlarged more than that in the comparative example. When the slit region is enlarged in such a manner, the region in which the motion of the liquid crystal molecules is controlled becomes wider by the amount of enlargement of the slit region, and the transverse electric field generated between the pixel electrode  25  and the opposite electrode  21  becomes strong and stable, so that the controllability of the liquid crystal molecules becomes favorable, and display contrast improves. 
         [0062]    Further, in the present embodiment, the overlap region  101  in which the gate line  11  and the opposite electrode hole  22  overlap is covered with the extension part  15   a  of the first contact  15 . Consequently, a leak electric field from the gate line  11  passing through the opposite electrode hole  22  and reaching the liquid crystal layer  31  is blocked by the part (extension part  15   a ) of the first contact  15 , and disturbance of the electric field is suppressed. 
         [0063]    Further, in the present embodiment, the region  28  other than the inner edge region  27  facing the overlap region  101  in the inner edge region surrounding the opposite electrode hole  22  also overlaps the other extension part  15   c  of the first contact  15  above the first contact  15 . Consequently, even if the electric field generated between the pixel electrode  25  and the opposite electrode  21  is disturbed in the region  28 , the part (extension part  15   c ) of the first contact  15  blocks the light. As a result, the part in which liquid crystal controllability is low is prevented from contributing to display. 
         [0064]    Further, in the present embodiment, since the pixel electrode  25  overlaps the region  28  in the opposite electrode  21 , disturbance of the electric field which occurs in the case where the region  28  is not covered with the pixel electrode  25  is suppressed. 
         [0065]    In the foregoing embodiment, the case where the region  28  other than the region  27  overlapped with the gate line  11  in the inner edge region of the opposite electrode hole  22  overlaps both of the pixel electrode  25  and the first contact  15  has been described. However, the invention is not limited thereto. The region  28  may be overlapped with at least one of the pixel electrode  25  and the extension part  15   a  of the first contact  15 . 
         [0066]    In addition, the liquid crystal display device  1  of the present embodiment having the configuration that the plane size of the pixel insulating film hole  24  is larger than that of the interlayer insulating film hole  20  has been described. However, the liquid crystal display device of the present invention may have a configuration that, as illustrated in  FIG. 7 , the plane size of the interlayer insulating film hole  20  is larger than that of the pixel insulting film hole  24 . Such a liquid crystal display device may also produce effects similar to those of the liquid crystal display device  1  of the aforementioned embodiment. 
         [0067]    The liquid crystal display device  1  of the present embodiment has been described with respect to the case where the inner edge position of the pixel insulating film hole  24  and that of the interlayer insulating film hole  20  are different from each other. However, as illustrated in  FIG. 8 , at least one of a pair of side faces of the interlayer insulating film hole  20  (vertically hatched part) and a pair of side faces of the pixel insulating film hole  24  (obliquely hatched part) may be in the same plane. In the case of  FIG. 8 , the side faces in the column direction out of the side faces of the interlayer insulating film hole  20  and the pixel insulating film hole  24  are in the same plane. In addition, in the case of  FIG. 8 , the width of the extension part  15   a  of the first contact  15  is smaller than that in the case of  FIG. 2 . Such a liquid crystal display device  1  may also produce effects similar to those of the liquid crystal display device  1  of the aforementioned embodiment. Further, the size and the position of the pixel insulating film hole  24  may be the same as those of the interlayer insulating film hole  20 . In this case, the pixel insulating film hole  24  and the interlayer insulating film hole  20  may be formed by a single process using a single etching mask. 
       Second Embodiment 
       [0068]      FIG. 9  is an enlarged view of a portion of the first contact  15  in a liquid crystal display device  2  according to a second embodiment. The same reference numerals are designated to components similar to those of the first embodiment, and their description will not be repeated or will be given briefly. In the liquid crystal display device  2  of the second embodiment, two more slits  41  (the second slit from the right side and the second slit from the left side) out of slits  41  formed in the pixel electrode  40  are longer than those of the first embodiment, and a part of the slits  41  overlaps the extension part  15   a  of the first contact  15 . In the second embodiment, four slits out of the slits  26  extend close to the gate  12   a  of the TFT  12 . Therefore, as compared with the liquid crystal display device  1  of the first embodiment, a hatched region X 2  in  FIG. 9  becomes an incident light transmittable region, and display brightness improves by the amount of the region. 
       Third Embodiment 
       [0069]      FIG. 10  is an enlarged view of a portion of the first contact  15  in a liquid crystal display device  3  according to a third embodiment. The liquid crystal display device  3  of the third embodiment is configured so that at least one of a side face in which the interlayer insulating film hole  20  is formed and a side face in which the pixel insulating film hole  24  is formed is in the same plane, and the slits  41  formed in the pixel electrode  40  are formed in a manner similar to those of the second embodiment illustrated in  FIG. 9 . 
         [0070]    When all of side faces of the interlayer insulating film hole  20  and the pixel insulating film hole  24  are formed in the same plane, that is, the plane size of the interlayer insulating film hole  20  and that of the pixel insulating film hole  24  are set to the same and the holes  20  and  24  are disposed in the same position, the holes  20  and  24  may be formed by single etching. A concrete example of the process is as follows. On the top face of the transistor protection film  18 , the first contact  15 , and the data line  16 , an insulating material which becomes the interlayer insulating film  19  is provided. After that, the opposite electrode  21  is formed as described above and, on the top face of them, an insulating material which becomes the pixel insulating film  23  is provided. Next, a mask is formed by using the photolithography technique. After that, an opening in the mask is etched to form a hole continuously penetrating from the interlayer insulating film  18  to the pixel insulating film  23 . 
         [0071]    When the photolithography process and the etching process are performed once as described above, the process is simplified, and one kind of a photomask prepared for the photolithography is sufficient. In addition, when the side face of the interlayer insulating film hole and that the pixel insulating film hole are continuous in the layer stack direction, the plane sizes of the holes  20  and  24  may be made smaller. In a manner similar to the above, the incident light transmittable region is enlarged, and transmittance is improved. 
         [0072]    Although some embodiments and modifications have been described above, the present invention is not limited to them but may be properly modified. For example, the shape of the opening in the pixel electrode is not limited to the linear slit shape but may be another opening shape such as a bent slit shape. The shape of the contact is not limited to square shape but may be rectangle shape or other shapes. 
         [0073]    The present application contains subject matter related to that disclosed in Japanese Priority Patent Application JP 2008-157229 filed in the Japan Patent Office on Jun. 16, 2008, the entire content of which is hereby incorporated by reference. 
         [0074]    Obviously many modifications and variations of the present invention are possible in the light of the above teachings. It is therefore to be understood that within the scope of the appended claims the invention may be practiced otherwise than as specifically described.