Abstract:
Provided are a backlight assembly with improved heat dissipation, and a liquid crystal display (LCD) having such a backlight assembly. The backlight assembly includes: a light guide plate; a light source unit disposed on a side of the light guide plate; an intermediate housing covering an upper surface of the light source unit; and a lower housing coupled to the intermediate housing to accommodate the light guide plate and the light source unit, wherein the lower housing includes: a light source unit-fixing frame to which the light source unit is fixed, the light source unit-fixing frame contacting an inner surface of the intermediate housing; and a body portion disposed under the light guide plate and coupled to the light source unit-fixing frame.

Description:
[0001]    This application is a Division of U.S. patent application Ser. No. 12/780,726, filed on May 14, 2010 which claims priority from Korean Patent Application No. 10-2009-0117186 filed on Nov. 30, 2009 in the Korean Intellectual Property Office, the disclosures of both said applications being incorporated herein by reference in their entireties. 
     
    
     BACKGROUND 
       [0002]    1. Field of Disclosure 
         [0003]    The present disclosure of invention relates to a display device, a thin-film transistor (TFT) structure, and a method of fabricating the TFT substrate, and more particularly, to a TFT based display device with maintained aperture ratio and minimized kickback voltage despite increased size of drain contact hole. The disclosure also relates to an Liquid Crystal Display (LCD) having a TFT array substrate that uses the here taught TFT structures, and a method of fabricating the LCD. 
         [0004]    2. Description of Related Technology 
         [0005]    Liquid crystal displays (LCDs) are one of the most widely used types of flat panel displays. Generally, an LCD includes two spaced apart substrates both having electrodes and a liquid crystal layer interposed between the substrates. In an LCD, voltages are applied to the electrodes to generate electric fields through the liquid crystal layer. The electric field determines an alignment of molecules in the liquid crystal layer, thereby controlling an amount of light that passes through light polarizing layers of the LCD. 
         [0006]    Of the two substrates included in an LCD, one is typically referred to as the thin-film transistor (TFT) array substrate and it includes a plurality of pixel units organized in an array format and each having one or more thin-film transistors (TFTs) and one or more pixel electrodes. Traditionally, the other substrate (common electrode substrate) contains a color filters layer. However, recently, research into a Color on Array (COA) structure has intensified wherein the CoA structure provides color filters on the TFT substrate instead of on the common electrode substrate. Part of the research is directed to ways to improve the planarization, alignment, and optical characteristics of LCDs using the CoA structure. In particular, research is being conducted on ways to improve planarization characteristics of TFT substrates having the COA structure in order to increase the reliability of the TFT substrate. One research direction looks at ways to increase the thickness of a planarization film as a way to improve the planarization characteristics of a CoA structure. 
         [0007]    However, when the thickness of the planarization film is increased, a width of a contact-providing through hole in the pixel unit structure generally needs to also increase. More specifically, it is a drain to pixel-electrode contact through hole that is provided in a light blocking or black-masked area of the pixel unit that generally needs to increase in size. As the hole size increases, however, a drain electrode beneath it also has to increase in size according to traditional design methodologies so as to assure proper registration with the widened hole. More specifically, when the contact hole in question is the one to the TFT drain and the area of the underlying drain electrode has to be increased to prevent the occurrence of an overlay miss between the drain electrode and the contact hole, several disadvantages flow from this result (from increased drain electrode area). 
         [0008]    Firstly, the value of an undesirable parasitic capacitance between the drain and gate nodes of the TFT tends to increase. Secondly, the increased drain electrode size operates to reduce an aperture ratio (e.g., a ratio of the light passing portion versus light blocking portions of each of the repeated pixel units in the LCD. The reduction in the aperture ratio can deteriorate image quality and waste backlighting power. Also the increased size of the drain contact hole can lead to undesired leakage of light around the contact hole area. 
       SUMMARY 
       [0009]    The present disclosure of invention provides methods of fabricating thin-film transistor (TFT) based pixel units having an increased or maintained aperture ratio and maintained or minimized parasitic capacitance between drain and gate nodes of the TFT so that excessive kick back voltage is suppressed. 
         [0010]    The present teachings are not restricted to just the embodiments set forth herein as examples. Various aspects of the present teachings will become more apparent to one of ordinary skill in the art to which the present teachings most closely pertain by referencing the detailed description as given below. 
         [0011]    According to an aspect of the present disclosure, there is provided a method of fabricating a TFT array substrate. The method includes: forming a gate electrode in a repeated pixel unit region of a substrate; forming a gate insulating film on the gate electrode; forming a semiconductor layer portion on the gate insulating film to overlap the gate electrode; forming a source electrode and a spaced apart drain electrode to overlap the semiconductor layer and to thus form a channel region; forming a channel passivating film that covers the exposed channel surface between the source and drain electrodes but does not cover the drain electrode, and forming a data insulating film on the source electrode and the drain electrode and patterning the data insulating film to form a through hole directed to contacting the drain electrode wherein part of the formed contact hole may overlap the passivated channel region and yet not create substantial deterioration of TFT performance. 
         [0012]    According to another aspect of the present disclosure, there is provided a TFT array substrate including: a gate electrode formed on a pixel region of a substrate; a gate insulating film formed on the gate electrode; a semiconductor layer formed on the gate insulating film to overlap the gate electrode; a source electrode and a drain electrode overlapping the semiconductor layer; and a data insulating film formed on the source electrode and the drain electrode, wherein part of a contact hole formed in the data insulating film may overlap the channel region. 
         [0013]    According to another aspect of the present disclosure, there is provided a liquid crystal display including: an insulating substrate; gate wiring formed on the insulating substrate and including a gate line and a gate electrode; a semiconductor pattern; data wiring including a data line, a source electrode, and a drain electrode which is separated from the source electrode; a passivation film formed on the data wiring and made of an organic material; and a contact hole formed through the passivation film and exposing a sidewall of the drain electrode so that connection to the pixel-electrode may include connection to the sidewall of the drain electrode. Other aspects will become clearer from the below detailed description. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0014]    The above and other aspects and features of the present disclosure of invention will become more apparent by describing in detail exemplary embodiments thereof with reference to the attached drawings, in which: 
           [0015]      FIG. 1  is a plan view of a thin-film transistor (TFT) substrate according to a first exemplary embodiment of the present disclosure; 
           [0016]      FIG. 2A  is a cross-sectional view of the TFT substrate taken along the line I-I′ of  FIG. 1 ; 
           [0017]      FIG. 2B  is an enlarged view of a portion ‘A’ in  FIG. 1 ; 
           [0018]      FIGS. 3 through 11  are cross-sectional views sequentially showing processes included in a method of fabricating a TFT substrate according to a second exemplary embodiment; 
           [0019]      FIG. 12  is a cross-sectional view showing the relationship between the TFT substrate according to the first exemplary embodiment and an upper substrate that faces the TFT substrate; 
           [0020]      FIG. 13  is a plan view of a TFT substrate according to a modified example of the first exemplary embodiment; 
           [0021]      FIG. 14A  is a cross-sectional view of the TFT substrate taken along the line II-II′ of  FIG. 13 ; 
           [0022]      FIG. 14B  is an enlarged view of a portion ‘B’ in  FIG. 13 ; 
           [0023]      FIG. 15  is a plan view of a TFT substrate according to a third exemplary embodiment; 
           [0024]      FIG. 16A  is a cross-sectional view of the TFT substrate taken along the line III-III′ of  FIG. 15 ; 
           [0025]      FIG. 16B  is an enlarged view of a portion ‘C’ in  FIG. 15 ; 
           [0026]      FIGS. 17 and 18  are cross-sectional views for explaining a method of fabricating a TFT substrate according to a fourth exemplary embodiment; 
           [0027]      FIG. 19  is a cross-sectional view showing the relationship between the TFT substrate according to the third exemplary embodiment and an upper substrate that faces the TFT substrate; 
           [0028]      FIG. 20  is a plan view of a TFT substrate according to a modified example of the third exemplary embodiment; 
           [0029]      FIG. 21A  is a cross-sectional view of the TFT substrate taken along the line IV-IV′ of  FIG. 20 ; 
           [0030]      FIG. 21B  is an enlarged view of a portion ‘D’ in  FIG. 20 ; 
           [0031]      FIG. 22  is a layout diagram of a display device according to a fifth exemplary embodiment; 
           [0032]      FIG. 23  is a cross-sectional view of the display device taken along the line V-V′ of  FIG. 22 ; 
           [0033]      FIG. 24  is a cross-sectional view of the display device taken along the line VI-VI′ of  FIG. 22 ; and 
           [0034]      FIGS. 25A and 25B  are enlarged views of a portion ‘E’ in  FIG. 22 . 
       
    
    
     DETAILED DESCRIPTION 
       [0035]    Advantages and features of devices formed in accordance with the present disclosure and methods of accomplishing the same may be understood more readily by reference to the following detailed description of exemplary embodiments and the accompanying drawings. The present teachings may, however, be embodied in many different forms and should not be construed as being limited to the exemplary embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete and will fully convey the concepts of the present teachings to those skilled in the relevant art. In some embodiments, well-known processing processes, well-known structures, and well-known technologies will not be specifically described in order to avoid ambiguous interpretations of the present teachings. Like reference numerals generally refer to like elements throughout the specification. 
         [0036]    Spatially relative terms, such as “below,” “beneath,” “lower,” “above,” “upper,” and the like, may be used herein for ease of description to describe one device or element&#39;s relationship to another device(s) or element(s) as illustrated in the drawings. It will be understood that the spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the drawings. For example, if the device in the figures is turned over, elements described as “below” or “beneath” other elements or features would then be oriented “above” the other elements or features. Thus, the exemplary term “below” can encompass both an orientation of above and below. The device may be otherwise oriented and the spatially relative descriptors used herein interpreted accordingly. 
         [0037]    The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the disclosure. As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises” and/or “comprising,” when used in this specification, specify the presence of stated components, steps, operations, and/or elements, but do not preclude the presence or addition of one or more other components, steps, operations, elements, and/or groups thereof. 
         [0038]    Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure pertains. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein. 
         [0039]    Hereinafter, a TFT substrate according to a first exemplary embodiment will be described in detail with reference to  FIGS. 1 through 2B .  FIG. 1  is a plan view of the TFT substrate according to the first exemplary embodiment.  FIG. 2A  is a cross-sectional view of the TFT substrate taken along the line I-I′ of  FIG. 1 .  FIG. 2B  is an enlarged view of a portion ‘A’ in  FIG. 1 . 
         [0040]    Referring to  FIGS. 1 through 2B , the TFT substrate includes various devices, such as thin-film transistors, which are formed on an insulating substrate  10 . The insulating substrate  10  may be a light-passing one such as made of glass, including a soda lime glass or a boro silicate glass, or of a plastic. 
         [0041]    Gate wiring, which delivers gate signals, is formed on the insulating substrate  10 . The gate wiring includes a gate line  22  which extends in a first direction, for example, a horizontal direction, and a gate electrode  24  which integrally protrudes from the gate line  22  and is included in a thin-film transistor. In the first exemplary embodiment, the case where just one gate line  22  extends through each unit pixel region of a given row is described. However, two gate lines may also be formed in each unit pixel region to transmit gate signals to different subpixels. In this case, two gate electrodes may also be formed in each pixel region to be adjacent respectively to data lines on both sides of that pixel which contains plural subpixels (or plural pixel-electrodes). 
         [0042]    In the first exemplary embodiment, each pixel region may be a bound region having its boundaries formed by adjacent gate lines  22  and adjacent data lines  56  intersecting therewith. 
         [0043]    A charge storage line (not shown), which delivers a common voltage to a charge storage electrode, may also be formed on the insulating substrate  10  in a layer level the same as that of the gate wirings. The storage line may extend in the horizontal direction to be substantially parallel to the gate line  22 . 
         [0044]    The signal conveying wirings (e.g., the gate lines  22  and their integrally protruding gate electrodes  24 , the storage lines, etc.) may be made of an aluminum (Al)-based metal, such as aluminum and/or an aluminum alloy, of a silver (Ag)-based metal, such as silver and a silver alloy, of a copper (Cu)-based metal such as copper and a copper alloy, of a molybdenum (Mo)-based metal such as molybdenum and a molybdenum alloy, of a chromium (Cr), or titanium (Ti) and/or tantalum (Ta) based metal. 
         [0045]    In addition, the signal conveying wirings may have multi-film structures composed of two or more conductive films (not shown) with different physical characteristics. One of the two conductive films may be made of metal with relatively low resistivity, such as an aluminum-based metal, silver-based metal or copper-based metal, in order to reduce a signal delay or a voltage drop of the signal conveying wiring. The other one of the conductive films may be made of a different material, in particular, a material having superior contact characteristics (e.g., ohmic contact characteristics) with zinc oxide (ZnO), indium tin oxide (ITO) and indium zinc oxide (IZO), such as molybdenum-based metal, chromium, titanium, or tantalum. Examples of multi-film structures include a chromium lower film and an aluminum upper film or an aluminum lower film and a molybdenum upper film. However, the present teachings are not limited thereto. The signal wirings may be made of various other metals and conductors (e.g., including light-passing conductors). 
         [0046]    A gate insulating film  30  is formed on the insulating substrate  10 , the gate wiring, and the storage line. The gate insulating film  30  may be made of a silicon oxide (SiOx) and/or a silicon nitride (SiNx) or a silicon oxynitride (SiOxNy). 
         [0047]    A semiconductor layer  42 , which is formed of hydrogenated amorphous silicon or polycrystalline silicon, is disposed on the gate insulating film  30 . The semiconductor layer  42  may have portions of various shapes. For example, the semiconductor layer portion  42  may be an island shape or may be formed as a linearly region. In the first exemplary embodiment, the semiconductor layer portion  40  is an island. The semiconductor layer portion  42  overlaps the area of the gate electrode  24 . 
         [0048]    Ohmic contact layer portions  44  and  45  formed of a contact enhancing material such as silicide or n+ hydrogenated amorphous silicon doped with n-type impurities in high concentration, may be disposed on the semiconductor layer  42 . That is, a pair of the ohmic contact layer portions  44  and  45  may be formed on the semiconductor layer portion  42 . 
         [0049]    Signal carrying wirings may be formed on the ohmic contact layer portions  44  and  45  and the gate insulating film  30 . 
         [0050]    The signal carrying wirings include the data line  56 , a source electrode  52  which branches off integrally from the data line  56 , and a drain electrode  54  which is shaped like an island and is separated from the source electrode  52  by a predetermined gap (channel gap) to thereby face the source electrode  52 . 
         [0051]    The data line  56  generally extends in a vertical direction, crosses the gate line  22  and the storage line, and delivers a predetermined data voltage for selective application to the pixel-electrode of the pixel unit. 
         [0052]    The source electrode  52  branches off integrally from the data line  56  toward the drain electrode  54 . A data line contacting terminal end (not shown) is formed at an end of the data line  56  and receives a data signal from another layer or an external source to transmit the data signal to the data line  56 . 
         [0053]    The data wiring may be formed of refractory metal such as chromium, molybdenum-based metal, tantalum, and titanium. In addition, the data wiring may have a multi-film structure composed of a lower film (not shown), which is formed of refractory metal, and an upper film (not shown), which is formed of a material with low resistivity and is disposed on the lower film. Examples of multi-film structures include a chromium lower film and an aluminum upper film or an aluminum lower film and a molybdenum upper film. Alternatively, the multi-film structure may be a three-film structure having molybdenum-aluminum-molybdenum films. 
         [0054]    The source electrode  52  overlaps at least part of the semiconductor layer  42 . In addition, the drain electrode  54  faces the source electrode  52  and overlaps at least another part of the semiconductor layer  42 . 
         [0055]    Referring to the magnified view in  FIG. 2B , a gate-controlled semiconductive first region of the semiconductor layer  42 , which region is between the source electrode  52  and one side (left side in  FIG. 2A ) of the drain electrode  54 , is defined as a first channel region CH_ 1 . In the first channel region CH_ 1 , a conductive channel through which electric charges can move, may be formed between the source electrode  52  and the drain electrode  54  when a turn-on gate voltage (V gON ) is applied to the gate electrode  24  and an appropriate data voltage is applied to the source electrode  52 . The thus formed, conductive channel may allow electric current to flow from the source electrode  52  to the drain electrode  54  so as to thereby charge the pixel-electrode to a desired potential level. 
         [0056]    In one embodiment, a width W 1  or diameter R 1  of the drain electrode  54  may be 6 μm or less. This width W 1  may be partially overlapped by a bottom portion of a drain contact hole  84 . If in this embodiment the width W 1  (or diameter R 1 ) of the drain electrode  54  is made greater than the 6 μm dimension, a corresponding aperture ratio of the pixel unit may be disadvantageously reduced. In this case, if the aperture ratio is reduced, the intensity of light emitted from light sources (not shown) in a backlight assembly (not shown) must be increased in order to secure a desired or standard luminance level out of the top side of the LCD. However, such an intensity increase may disadvantageously increase the overall power consumption of a liquid crystal display (LCD). Thus, the width W 1  or diameter R 1  of the drain electrode  54  should be 6 μm or less in this embodiment in order to prevent the undesired increase in the overall power consumption of the LCD. 
         [0057]    The ohmic contact layer portions  44  and  45  are interposed between the semiconductor layer portion  42  thereunder and the source and drain electrodes  52  and  54  thereon to establish ohmic connections and reduce contact resistance between them. 
         [0058]    A channel passivation layer  61  is formed in the region between the source electrode  52  and the drain electrode  54 . The channel passivation layer  61  may be made of an inorganic matter such as SiNx and/or SiOx and/or SiOxNy. The channel passivation layer  61  protects exposed top surface portions of the semiconductor layer  42 . 
         [0059]    The channel passivation layer  61  is pre-patterned such that it does not cover top surfaces of the source electrode  52  and the drain electrode  54 . Accordingly, at least the full top surface area of the drain electrode is available for contact therewith by way of a to-be formed, drain contact hole. (In one embodiment described below, sidewalls of the drain electrode are also available for contact therewith by way of a to-be formed, drain contact hole.) Because the channel passivation layer  61  is pre-patterned, when the drain electrode contacting through hole  84  is later formed through a data insulating film  80  (which will be described later) there is no need to first selectively etch through the passivation layer  61  to expose the drain electrode  54 . Thus mass production fabrication is greatly simplified. A method for forming the pre-patterned channel passivation layer  61  will be detailed below (for example in reference to  FIG. 8 ). 
         [0060]    One of red, green, and blue color filters  70  is formed on each pixel region defined by the intersection of the gate line  22  and the data line  56 . (Other color filters, e.g., white, cyan, etc. may also be used.) 
         [0061]    Each of the color filters  70  passes light in its respectively predetermined and different wavelengths range. The color filters  70  may be arranged for example in a stripe, mosaic, or delta pattern. 
         [0062]    The color filters  70  may be made of an organic material having photosensitivity, such as photoresist. The color filters  70  may be formed to a uniform thickness or formed in a stepped manner to have a predetermined step height. Each of the color filters  70  may be made of a red organic material which primarily passes light of a red wavelength, a blue organic material which primarily passes light of a blue wavelength, or a green organic material which primarily passes light of a green wavelength. 
         [0063]    The data insulating film  80  (also planarization film  80  herein) is formed on the source electrode  52 , the drain electrode  54 , the passivation layer  61 , and the color filters  70 . The data insulating film  80  may be made of an organic photoresist material having superior planarization characteristics. Alternatively, the data insulating film  80  may be made of SiNx. The passivation layer  61  and the data insulating film  80  may be made of different materials. For example, when the passivation layer  61  is made of SiOx, the data insulating film  80  may be made of an organic material or SiNx. The data insulating film  80  may be formed to a thickness of approximately 3 μm to fully cover the color filters  70  so that the color filters  70  do not cause changes of distance between the overlying pixel-electrode  90  and a common electrode in the other substrate. Since the data insulating film  80  fully covers the color filters  70 , it can have superior planarization characteristics. 
         [0064]    The contact hole  84  is formed through the data insulating film  80  so as to extend to underlying portions of the drain electrode  54  and of the passivation layer  61 . The pixel electrode  90 , which will be described more fully later, and the drain electrode  54  are electrically connected to each other by the contact hole  84 . Accordingly, a data signal can be transmitted to the pixel electrode  90  from the data line  56  by passing through the drain electrode  54  of the corresponding TFT. Here, part of the contact hole  84  may overlap the channel region (e.g., CH_ 2 ) but it is isolated from the overlapped portion of the channel region by the passivation layer  61 . 
         [0065]    As the thickness of the data insulating film  80  increases, a width of the contact hole  84  also tends to increase, thereby increasing the likelihood of an overlay miss between the drain electrode  54  and the bottom of the tapered contact hole  84 . If the passivation layer  61  were not present, such an overlay miss may result in an internal short circuit, that is, may cause the pixel electrode  90  to directly connect to the semiconductor layer  42  such that a predetermined channel gap is made too short or shorted out completely and the TFT fails to operate as intended. To reduce the possibility of such internal short circuits, the area of the drain electrode  54  is typically increased in accordance with an increase in the width of the bottom of the contact hole  80 . However, an increase in the area of the drain electrode  54  may result in an increase in a value of a parasitic capacitance Cgd between the drain ( 54 ) and the gate ( 24 ) nodes of the TFT, thereby increasing an undesirable kickback voltage of the TFT. (The kickback voltage tends to increase when the Cgd capacitance increases.) In addition, an increase in the area of the drain electrode  54  may result in a reduction in the aperture ratio. Consequently, image quality of a display device may deteriorate. 
         [0066]    According to the present disclosure however, the passivation layer  61  is formed in the region between the source electrode  52  and the drain electrode  54  above the semiconductor layer  42 . Thus, even when an overlay miss occurs; as is shown schematically in  FIG. 2A , between the bottom of the contact hole  84  and the exposed upper surface of the drain electrode  54 , the misalignment may not cause the internal short circuit conditions described above. That is, the passivation layer  61  is present to prevent the drain-contacting portion of the pixel electrode  90  from directly contacting the semiconductor layer  42  to thus shorten the effective length of the TFT channel. Note that although the plan view of  FIG. 2B  makes it appear as if the channel length is being shortened in region CH_ 1 , this is not the case because the bottom of the drain contact hole is spaced apart from the channel surface by the thickness of the passivation layer  61 . Therefore, according to the present disclosure, even when the width of the contact hole  84  increases in accordance with the increase in the thickness of the data insulating film  80 , there is no need to correspondingly increase the area of the drain electrode  54  to accommodate for possible misalignment of the bottom of the contact hole. Accordingly, the value of the parasitic capacitance Cgd between the drain node ( 54 ) and the gate node ( 24 ) does not significantly increase. Consequently, an undesirable increase in the kickback voltage and an undesirable reduction in the aperture ratio can be substantially prevented. 
         [0067]    After the drain contact hole  84  is formed, for example as a tapered hole, the pixel electrode  90  is formed on the data insulating film  80 . The pixel electrode  90  may be formed of a transparent conductor, such as ITO or IZO, or of a reflective conductor such as aluminum depending on whether the LCD is a light through-passing kind or a light reflecting kind. The pixel electrode  90  is electrically connected to the drain electrode  54  by way of a portion of the deposited pixel-electrode material extending through the contact hole  84  to make at least partially overlapping contact with the upper surface of the drain electrode  54 . The drain contacting portion of the pixel electrode  90  may be disposed on/above the drain electrode  54  and on the adjacent part of the passivation layer  61 . That is, the passivation layer  61  is interposed between the pixel electrode  90  and the semiconductor layer  42 . Accordingly, even when an overlay miss occurs between the bottom of the contact hole  84  and the drain electrode  54 , this misalignment does not cause the above-described internal short circuit phenomenon to occur (e.g., effective shortening of the TFT channel length) due to the presence of the short-preventing passivation layer  61 . 
         [0068]    A column spacer (not shown) may be formed on the TFT substrate. The column spacer may be used to maintain a substantially constant cell gap between an upper substrate and the TFT substrate. 
         [0069]    Hereinafter, a method of fabricating a TFT substrate according to a second exemplary embodiment will be described in detail with reference to  FIGS. 3 through 12 .  FIGS. 3 through 11  are cross-sectional views sequentially showing processes included in the method of fabricating a TFT substrate according to the second exemplary embodiment. For simplicity, elements having the same functions as those shown in the drawings for the first exemplary embodiment are indicated by like reference numerals, and thus their description will be omitted or simplified. 
         [0070]    Referring to  FIG. 3 , a gate layer wiring pattern  22 / 24 , which includes a patterned gate line  22  and a patterned gate electrode  24 , and a patterned storage line (not shown) are formed on a light-passing insulating substrate  10 . 
         [0071]    The gate wiring layer may be formed by, e.g., blanket sputtering of the appropriate conductive materials. Then, the deposited gate wiring layer may be patterned by a wet-etching process or a dry-etching process. In the wet-etching process, an etchant, such as phosphoric acid, nitric acid or acetic acid, may be used in combination with an etchant resistant mask. In the dry-etching process, a fluorine-based etching gas, such as Cl 2  or BCl 3 , may be used in combination with a plasma resistant mask whose pattern is defined with use of appropriate photolithography. 
         [0072]    Referring to  FIG. 4 , next a gate insulating film  30  is formed on the insulating substrate  10 , the patterned gate wiring layer  22 / 24 . The gate insulating film  30  may be blanket formed by plasma enhanced chemical vapor deposition (PECVD) or reactive sputtering. 
         [0073]    Referring to  FIGS. 5 and 6 , next a hydrogenated amorphous silicon layer  40 , an n+ hydrogenated amorphous silicon layer  41  that is doped with n-type impurities in high concentration, and a conductive layer  50  are formed by stacking of respective conductive materials for forming the data wring layer are sequentially disposed on the gate insulating film  30 . The hydrogenated amorphous silicon layer  40  and the n+ hydrogenated amorphous silicon layer  41  doped with n-type impurities in high concentration may be formed by PECVD or chemical vapor deposition (CVD). In addition, the conductive layer  50  may be formed by sputtering. 
         [0074]    Next (between  FIGS. 5 and 6 ), photoresist is coated on the conductive layer  50  and then developed to form photoresist patterns (not shown) for patterning in one step the hydrogenated amorphous silicon layer  40 , the n+ hydrogenated amorphous silicon layer  41  doped with n-type impurities in high concentration, and the conductive layer  50 . Then, the hydrogenated amorphous silicon layer  40 , the n+ hydrogenated amorphous silicon layer  41  doped with n-type impurities in high concentration, and the conductive layer  50  are etched in one step using the photoresist patterns (not shown) as a mask, thereby forming a semiconductor layer  42 , an ohmic contact layer pattern  43 , and a conductive layer pattern  51 , respectively as shown in  FIG. 6 . 
         [0075]    Thereafter, new photoresist patterns  102  and  103  are formed on the conductive layer pattern  51  as shown in  FIG. 6  for the purpose of next patterning the ohmic contact layer pattern  43  and the conductive layer pattern  51 . The left and right side photoresist pattern portions  102  are used to pattern a corresponding portion of the conductive layer pattern  51  into a semi-circular shaped source electrode  52  (see  FIG. 2B ). On the other hand, the middle photoresist pattern  103  is used to pattern another portion of the conductive layer pattern  51  into the centrally located drain electrode  54 . Although not shown in  FIG. 6 , the outer photoresist pattern portions  102  extend to also cover a leg portion of the Y-shaped source electrode  52  of  FIG. 2B  and portions  102  yet further extend to continuously surround the area where the color filter will be formed. The photoresist patterns  102  (and  103 ) are formed to a height sufficient to allow them to also serve as barrier ribs for containing color filter resin in an inkjet method that is used to later form the color filters  70  as will be described later. In addition, the photoresist patterns  102  and  103  may be inversely tapered (e.g., shaped as downward pointing frusto triangles in the cross section view) such that they can be easily exfoliated in a lift-off process which will be described later. 
         [0076]    Referring next to  FIG. 7 , the conductive layer pattern  51  is patterned using the photoresist pattern  102  and  103  as an etch mask, thereby forming the source electrode  52  and the drain electrode  54 . Here, the drain electrode  54  may be formed to a width (indicated by reference character ‘W 1 ’ in  FIG. 2A ) or diameter (indicated by reference character ‘R 1 ’ in  FIG. 2B ) of 6 μm or less. 
         [0077]    The ohmic contact layer pattern  43  is also patterned at the same time as the conductive layer pattern  51 . As a result, a patterned ohmic contact layer  44 , which is overlapped by a bottom surface of the source electrode  52 , and a patterned ohmic contact layer  45 , which is overlapped by a bottom surface of the drain electrode  54 , are formed. Since the source electrode  52  and the drain electrode  54  are formed above the semiconductor layer  42  and in spaced apart relation, a channel region CH_ 1  is formed in a region of the semiconductor layer  42  which is not overlapped by the source electrode  52  and the drain electrode  54 . 
         [0078]    Referring to  FIG. 8 , while the photoresist patterns  102  and  103  are still in place, an insulating material is blanket deposited on all up facing and exposed surfaces of the resultant structure of  FIG. 7  for example by PECVD or CVD deposition, thereby forming passivation layer regions  61  and  63  that do not overlap the source and drain electrodes,  52  and  54 . The deposited insulating material may be SiO2 or SiNx. Due to the photoresist patterns  102  and  103  still being formed on the upward facing tops of the source electrode  52  and the drain electrode  54 , the deposited insulating material that is stacked on upward facing top surfaces is not directly stacked on top surfaces of the source electrode  52  and the drain electrode  54  due to the photoresist patterns  102  and  103 . Instead, the insulating material is stacked on the top surfaces of the photoresist patterns  102  and  103  as an insulating material layers  62  and  64 . That is, the passivation layer regions  61  and  63  do not extend to directly cover the top surfaces of the source electrode  52  and the drain electrode  54 . The full top surface area of the drain electrode  54  as well as optionally part of the sidewall surface area of the drain electrode  54  are left available for later contact with the pixel-electrode after the drain contact hole is formed ( 84  in  FIG. 11 ). 
         [0079]    When the photoresist patterns  102  and  103  are inversely tapered as shown in  FIG. 8 , the blanket deposited insulating material is not stacked on the down facing side walls of the photoresist patterns  102  and  103 , and there is a break in continuity between passivation layer regions  61  and  63 , thereby making it easy to later exfoliate the photoresist patterns  102  and  103  from the structure. 
         [0080]    Referring to  FIG. 9 , next drops of a colored organic material are selectively deposited, for example by ink jet spraying over the resultant structure of  FIG. 8  by using, e.g., an inkjet printing device (not shown). In this inkjet deposition method, the still present, photoresist patterns  102  and  103  are used as barrier ribs for containing the liquid colored organic material before it is hardened. In other words, each respective pixel region is surrounded by the photoresist patterns  102  and  103  when it is sprayed and it is filled with the colored organic material. There is no need to spray the colored organic material over the region between the source electrode  52  and the drain electrode  54  in which no image is displayed. 
         [0081]    Specifically, to form the color filters  70  using an inkjet printing device, a red organic liquid material is sprayed over and thus fills a pixel region surrounded by the photoresist patterns  102  and  103  while the inkjet printing device is moved in a predetermined direction over the pixel region that is predetermined to be a red pixel unit. In the case of an RGB striped pattern being used, the red organic material is sprayed over one in every three pixel regions arranged in the direction in which the inkjet printing device is moved. Then, green and blue organic materials are also sprayed over the other pixel regions in the same way. If the inkjet printing device can spray all of the three colored organic materials, it may move over pixel regions while alternately spraying the three colored organic materials. 
         [0082]    A colored organic material when it is sprayed is a hardenable liquid material. However, since the sprayed colored organic material has a sufficient amount of viscosity and it is surrounded by the photoresist pattern  102 , it can stably remain within a pixel region. In the inkjet method, the photoresist patterns  102  and  103 , which are formed to pattern the data wiring and the ohmic contact layers  44  and  45 , can be used as ink jet barrier ribs. Thus, a process for separately forming barrier ribs can be omitted, which, in turn, simplifies the entire fabrication process. 
         [0083]    The liquid, colored organic material plus solvent which is filled between the photoresist patterns  102  and  103  is dried and solidified for example by heat treatment or ultraviolet radiation. As a result, one of the red, green and blue filters  70  is formed in each pixel region. 
         [0084]    Referring to  FIG. 10 , the photoresist patterns  102  and  103  formed on the source electrode  52  and the drain electrode  54  are removed (exfoliated). Here, the insulating material layers  62  and  64  on the top surfaces of the photoresist patterns  102  and  103  are lifted off and thus removed. Accordingly, the passivation layers  61  and  63  no longer cover the top surfaces of the source electrode  52  and the drain electrode  54 . Thus, the top surfaces of the source electrode  52  and the drain electrode  54  are exposed. In one embodiment, a top surface cleaning process may be used to assuredly remove left behind micro remnants of the photoresist material of patterns  102  and  103 . In other words, the effect that can be achieved when the passivation layer regions  61  and  63  are formed, that the tops of the source electrode  52  and the drain electrode  54  are not covered by the passivation layer material ( 61 ,  63 ). Since no additional photoresist process is now needed for selectively exposing the top surfaces of the source electrode  52  and the drain electrode  54 , the entire fabrication process can be simplified. 
         [0085]    Referring to  FIG. 11 , a data insulating film  80  is formed on the source electrode  52 , the drain electrode  54 , the color filters  70 , and the passivation layer  61 . The data insulating film  80  may be made of an organic material to have superior planarization characteristics. Alternatively or additionally, the data insulating film  80  may be made of SiNx. Planarization of film  80  by CMP or the like may be carried out before and/or after the drain contact hole  84  is formed. After the data insulating film  80  is deposited, the drain contact hole  84  is formed in the data insulating film  80  to expose at least part of the drain electrode  54 . Here, an overlay miss may occur between the bottom of the contact hole  84  (optionally down tapered hole  84 ) and the drain electrode  54 , thereby causing the bottom of the contact hole  84  to expose part of the passivation layer  61  between the source and drain electrodes. That is, part of the contact hole  84  may overlap the top of the passivation layer  61  that covers the channel region CH_ 1 . 
         [0086]    According to the present disclosure, even when an overlay miss occurs, it is not accompanied by significant problems, as described above because the target missing portion of the downward extending pixel-electrode is vertically spaced apart from the semiconductor surface by the thickness of the passivation layer  61 . 
         [0087]    Referring back to  FIG. 2 , a transparent conductive material, such as ITO or IZO, is stacked on the data insulating film  80  by sputtering and then patterned to form a pixel electrode  90  which is electrically connected to the drain electrode  54  by passage through the contact hole  84 . 
         [0088]      FIG. 12  is a cross-sectional view showing the relationship between the TFT substrate according to the first exemplary embodiment and the upper substrate that faces the TFT substrate. Referring to  FIG. 12 , the upper substrate includes a base substrate  200 , a black matrix  210 , an overcoat layer  220 , and a common electrode  230 . 
         [0089]    The black matrix  210  may be made of metal (metal oxide), such as chromium and chromium oxide, or organic black resist. The black matrix  210  may overlap a thin-film transistor formed on the TFT substrate. Accordingly, the black matrix  210  can prevent leakage of light, thereby improving image quality. According to the present disclosure, the contact hole  84  is formed in a region overlapped by the black matrix  210 . The size of the black matrix  210  does not need to be increased when the thickness of the planarization layer  80  is increased because the present design can tolerate misalignment between the drain contact hole  84  and the drain electrode  54 . Thus, an aperture ratio of the device need not be decreased when planarization thickness is increased, where decrease of the aperture ratio disadvantageously reduces image quality and/or increases backlighting power consumption. 
         [0090]    Hereinafter, a TFT substrate according to a modified example of the first exemplary embodiment will be described with reference to  FIGS. 13 through 14B .  FIG. 13  is a plan view of the TFT substrate according to the modified example of the first exemplary embodiment of the present invention.  FIG. 14A  is a cross-sectional view of the TFT substrate taken along the line II-II′ of  FIG. 13 .  FIG. 14B  is an enlarged view of a portion ‘B’ in  FIG. 13 . For simplicity, elements having the same functions as those shown in the drawings for the first exemplary embodiment are indicated by like reference numerals, and thus their description will be omitted or simplified. 
         [0091]    Referring to  FIG. 13 , a source electrode  55  according to the modified example of the first exemplary embodiment fully surrounds the drain electrode  54 . Accordingly, a thin-film transistor according to the modified example of the first exemplary embodiment has a greater effective channel width than a thin-film transistor according to the first exemplary embodiment and thus can exhibit lower source to drain resistance when turned on and can provide better operation performance. 
         [0092]    A method of fabricating a TFT substrate according to a modified example of the second exemplary embodiment is substantially identical to the method of fabricating a TFT substrate according to the second exemplary embodiment except that a source electrode  55  is formed to fully surround the drain electrode  54 , and thus a detailed description thereof will not be repeated. 
         [0093]    Hereinafter, a TFT substrate according to a third exemplary embodiment of the present invention will be described in detail with reference to  FIGS. 15 through 16B .  FIG. 15  is a plan view of the TFT substrate according to the third exemplary embodiment of the present invention.  FIG. 16A  is a cross-sectional view of the TFT substrate taken along the line III-III′ of  FIG. 15 .  FIG. 16B  is an enlarged view of a portion ‘C’ in  FIG. 15 . For simplicity, elements having the same functions as those shown in the drawings for the first exemplary embodiment are indicated by like reference numerals, and thus their description will be omitted or simplified. The TFT substrate according to the third exemplary embodiment is identical to the TFT substrate according to the first exemplary embodiment except for the following features. 
         [0094]    In the TFT substrate according to the third exemplary embodiment, a passivation layer  65  covers a source electrode  52  and a drain electrode  54 . In addition, a contact hole  84  is formed in the passivation layer  65  and a data insulating film  80 . Here, the contact hole  84  overlaps a channel region CH_ 3 . Accordingly, the channel region CH_ 3  of a semiconductor layer  42  is exposed. Thus, part of a pixel electrode  90  may extend to directly contact the semiconductor layer  42 . At the same time the pixel electrode  90  of this embodiment contacts the full sidewall of drain electrode  54 . 
         [0095]    Hereinafter, a method of fabricating a TFT substrate according to a fourth exemplary embodiment will be described with reference to  FIGS. 17 through 19 .  FIGS. 17 and 18  are cross-sectional views for explaining the method of fabricating a TFT substrate according to the fourth exemplary embodiment of the present invention. For simplicity, elements having the same functions as those shown in the drawings for the first exemplary embodiment are indicated by like reference numerals, and thus their description will be omitted or simplified. The method of fabricating a TFT substrate according to the fourth exemplary embodiment is identical to the method of fabricating a TFT substrate according to the second exemplary embodiment except for the following features. 
         [0096]    Referring to  FIG. 17 , a source electrode  52  and a drain electrode  54  are formed on a substrate, and an insulating material is stacked on the substrate by PECVD or CVD, thereby forming a passivation film  60 . Here, the insulating material may be SiO2 or SiNx. 
         [0097]    Next, a data insulating film  80  is formed on the resultant structure of  FIG. 17 . After the data insulating film  80  is formed, the data insulating film  80  and the passivation film  60  are patterned to form a contact hole  84 . Here, part of the contact hole  84  may overlap a channel region CH_ 3  of a semiconductor layer  42 . Unlike in the second exemplary embodiment, in the fourth exemplary embodiment, the passivation film  60 ′ is patterned so that the later formed contact hole  84  extends through the passivation film  60 ′ to expose part of the semiconductor layer  42 . In other words, the passivation film  60 ′ is intentionally patterned so that part of the semiconductor layer  42  is exposed. The passivation film  60 ′ having the contact hole  84 ′ formed therethrough will be referred to as a passivation layer  65 . 
         [0098]    When the contact hole  84 ′ is formed, the passivation film  60  on the semiconductor layer  42  is etched. Thus, when the passivation film  60  is etched to form the contact hole  84 , it may have a different etch selectivity from the semiconductor layer  42  in order to prevent the semiconductor layer  42  from being etched. In addition, when the data insulating film  80  is etched to form the contact hole  84 , it may have a different etch selectivity from the semiconductor layer  42  in order to prevent the semiconductor layer  42  from being etched. 
         [0099]      FIG. 19  is a cross-sectional view showing the relationship between the TFT substrate according to the third exemplary embodiment and an upper substrate that faces the TFT substrate. Features shown in  FIG. 19  are substantially identical to those shown in  FIG. 12  except that the TFT substrate according to the third exemplary embodiment is applied, and thus a detailed description thereof will not be repeated. 
         [0100]    Hereinafter, a TFT substrate according to a modified example of the third exemplary embodiment of the present invention will be described with reference to  FIGS. 20 through 21B .  FIG. 20  is a plan view of the TFT substrate according to the modified example of the third exemplary embodiment.  FIG. 21A  is a cross-sectional view of the TFT substrate taken along the line IV-IV′ of  FIG. 20 .  FIG. 21B  is an enlarged view of a portion ‘D’ in  FIG. 20 . For simplicity, elements having the same functions as those shown in the drawings for the third exemplary embodiment are indicated by like reference numerals, and thus their description will be omitted or simplified. 
         [0101]    Referring to  FIG. 20 , a source electrode  55  according to the modified example of the third exemplary embodiment fully surrounds the drain electrode  54 . Accordingly, a thin-film transistor according to the modified example of the third exemplary embodiment has a greater channel width than a thin-film transistor according to the third exemplary embodiment and thus exhibits better operation performance. 
         [0102]    A method of fabricating a TFT substrate according to a modified example of the fourth exemplary embodiment of the present invention is substantially identical to the method of fabricating a TFT substrate according to the fourth exemplary embodiment except that a source electrode  55  is formed to fully surround the drain electrode  54 , and thus a detailed description thereof will not be repeated. 
         [0103]    Hereinafter, a display device  1  according to a fifth exemplary embodiment will be described in detail with reference to  FIGS. 22 through 25B .  FIG. 22  is a layout diagram of the display device  1  according to the fifth exemplary embodiment.  FIG. 23  is a cross-sectional view of the display device  1  taken along the line V-V′ of  FIG. 22 .  FIG. 24  is a cross-sectional view of the display device  1  taken along the line VI-VI′ of  FIG. 22 .  FIGS. 25A and 25B  are enlarged views of a portion ‘E’ in  FIG. 22 . 
         [0104]    Referring to  FIGS. 22 through 24 , the display device  1  according to the fifth exemplary embodiment includes a first display substrate  100 , a second display substrate  200 , a liquid crystal layer  300 , and a colored column spacer  501 . 
         [0105]    The first display substrate  100  includes an insulating substrate  10 , gate wiring, a gate insulating film  30 , a semiconductor pattern  42 , ohmic contact patterns  46  and  47 , data wiring, a passivation film  70 , a contact hole  77 , and a pixel electrode  82 . 
         [0106]    The insulating substrate  10  may be made of a light-transmissive and heat-resistant material such as transparent glass or plastic. 
         [0107]    The gate wiring is formed on the insulating substrate  10  in a first direction, for example, a horizontal direction. The gate wiring includes a plurality of gate lines  22  which deliver gate signals, a gate electrode  26  which integrally protrudes from each of the gate lines  22 , and a gate line end terminal (not shown) which is formed at an end of each of the gate lines  22  and receives a gate signal from another layer or an external source to transmit the gate signal to each of the gate lines  22 . The gate electrode  24 , a source electrode  65  and a drain electrode  66 , which will be described later, form three terminals of a thin-film transistor. 
         [0108]    The gate wiring (i.e., the gate lines  22  and the gate electrode  24 ) may be made of an aluminum (Al)-based metal, such as aluminum and an aluminum alloy (e.g., Al, AlNd, AlCu, etc.), silver (Ag)-based metal, such as silver and a silver alloy, copper (Cu)-based metal such as copper and a copper alloy, molybdenum (Mo)-based metal such as molybdenum and a molybdenum alloy (e.g., Mo, MoN, MoNb, etc.), chromium (Cr), titanium (Ti) or tantalum (Ta). 
         [0109]    In addition, the gate wiring may have a multi-film structure composed of two conductive films (not shown) with different physical characteristics. One of the two conductive films may be made of metal with low resistivity, such as aluminum-based metal, silver-based metal or copper-based metal, in order to reduce a signal delay or a voltage drop of the gate wiring. The other one of the conductive films may be made of a different material, in particular, a material having superior contact characteristics with ITO and IZO, such as molybdenum-based metal, chromium, titanium, or tantalum. Examples of multi-film structures include a chromium lower film and an aluminum upper film or an aluminum lower film and a molybdenum upper film. However, the present teachings are not limited thereto. The gate wiring may be made of various other metals and conductors. 
         [0110]    The gate insulating film  30  is formed on the gate wiring and portions of the insulating substrate  10  which are exposed by the gate wiring. The gate insulating film  30  may be made of an inorganic insulating material such as SiOx and SiNx, or may be made of an organic insulating material such as benzocyclobutene (BCB), an acrylic material, and polyimide. The gate insulating film  30  covers the gate wiring (i.e., the gate lines  22  and the gate electrode  24 ). In particular, the gate insulating film  30  is formed on the entire surface of the insulating substrate  10 , including a pixel region in which the pixel electrode  82  is formed. Here, a pixel region may be understood as a region which is defined by the gate wiring and the data wiring and through which light emitted from a backlight assembly (not shown) of the display device  1  passes. 
         [0111]    The semiconductor pattern  42 , which is made of hydrogenated amorphous silicon, polycrystalline silicon or a conductive organic material, is formed on a portion of the gate insulating film  30 . 
         [0112]    The semiconductor pattern  42  may have various shapes. For example, the semiconductor pattern  42  may be an island or may be formed linearly. If the semiconductor pattern  42  is shaped like an island as in the current exemplary embodiment, it may be overlapped by part of a source electrode  57  and part of a drain electrode  59  above the gate electrode  24 . The shape of the semiconductor pattern  42  may not be limited to an island. 
         [0113]    The ohmic contact patterns  46  and  47  may be formed on the semiconductor pattern  42 . The ohmic contact patterns  46  and  47  are made of silicide, n+ hydrogenated amorphous silicon which is doped with n-type impurities in high concentration, or a material doped with p-type impurities, such as ITO. The ohmic contact patterns  46  and  47  are formed in pairs on the semiconductor pattern  42  and improve contact characteristics between the source electrode  57  and the semiconductor pattern  42  and between the drain electrode  59  and the semiconductor pattern  42 . When the contact characteristics between the source electrode  57  and the semiconductor pattern  42  and between the drain electrode  59  and the semiconductor pattern  42  are good enough, the ohmic contact patterns  46  and  47  may be omitted. 
         [0114]    On the resultant structure including the ohmic contact patterns  55  and  56 , the data wiring, which includes a data line  56 , the source electrode  57 , the drain electrode  59  and a data line end terminal (not shown), is formed. 
         [0115]    The data line  56  extends in a second direction, for example, a vertical direction. In addition, the data line  56  is insulated from each of the gate lines  22  and crosses each of the gate line  22 . 
         [0116]    The source electrode  57  integrally protrudes from the data line  56  in the form of a branch and extends onto the semiconductor pattern  42 . The data line end terminal (not shown) is formed at an end of the data line  56 . The data line end terminal receives a data signal from another layer or an external source and delivers the received data signal to the data line  56 . 
         [0117]    The source electrode  57  at least partially overlaps the semiconductor pattern  42 . The drain electrode  59  is separated from the source electrode  57  and is disposed above the semiconductor pattern  42  to face the source electrode  57  with respect to the gate electrode  24 . The semiconductor pattern  42  is exposed in the gap between the source electrode  57  and the drain electrode  59 . A thin-film transistor is a three-terminal device composed of the gate electrode  24 , the source electrode  57 , and the drain electrode  59 . In addition, a thin-film transistor is a switching device that allows electric current to flow between the source electrode  57  and the drain electrode  59  when a voltage is applied to the gate electrode  24 . 
         [0118]    The drain electrode  59  may include a first drain electrode portion  59 _ 1  and a second drain electrode portion  59 _ 2  which extends from the first drain electrode portion  59 _ 1  toward the source electrode  57 . The first drain electrode portion  59 _ 1  may be formed as a pattern relatively wider than the second drain electrode portion  59 _ 2 . The second drain electrode portion  59 _ 2  may be formed as a bar-shaped pattern that extends from the first drain electrode portion  59 _ 1  toward the source electrode  57 . 
         [0119]    The data wiring (i.e., the data line  56 , the source electrode  57 , and the drain electrode  59 ) may be a single film or multiple films which is/are made of one or more of Al, an Al alloy (e.g., Al, AlNd, AlCu or the like), Cr, a Cr alloy, Mo, a Mo alloy (e.g., Mo, MoN, MoNb or the like), Ta, a Ta alloy, Ti and a Ti alloy. For example, the data wiring may be made of refractory metal such as Cr, Mo-based metal, Ta and Ti. In addition, the data wiring may be formed of refractory metal such as chromium, molybdenum-based metal, tantalum, and titanium. In addition, the data wiring may have a multi-film structure composed of a lower film (not shown), which is formed of refractory metal, and an upper film (not shown) which is formed of a material with low resistivity and is disposed on the lower film. Examples of multi-film structures include a chromium lower film and an aluminum upper film and an aluminum lower film and a molybdenum upper film. Alternatively, the multi-film structure may be a three-film structure having molybdenum-aluminum-molybdenum films. 
         [0120]    The passivation film  70  is formed on the data wiring (i.e., the data line  56 , the source electrode  57 , and the drain electrode  59 ) and exposed portions of the gate insulating film  30 . The passivation film  70  may be made of an inorganic material such as silicon nitride or silicon oxide, an organic material having photosensitivity and superior planarization characteristics, or a low-k dielectric material formed by PECVD, such as a-Si:C:O or a-Si:O:F. 
         [0121]    The contact hole  77 , which exposes the drain electrode  59 , is formed in the passivation film  70 . The contact hole  77  exposes part of the first drain electrode portion  59 _ 1  and part of the second drain electrode portion  59 _ 2 . In addition, the contact hole  77  exposes a portion of the gate insulating film  30  which is located in a region adjacent to where the first drain electrode portion  59 _ 1  meets the second drain electrode portion  59 _ 2 . That is, since the first drain electrode portion  59 _ 1  is relatively wider than the second drain electrode portion  59 _ 2 , a portion of the gate insulating film  30  in a peripheral region of the second drain electrode portion  59 _ 2  may be exposed by the contact hole  77 . 
         [0122]    The pixel electrode  82  is formed on the passivation film  70  which is located in a pixel region and is connected to the drain electrode  59  by the contact hole  77 . The contact hole  77  exposes a portion of the first drain electrode portion  59 _ 1  and a portion of the second drain electrode portion  59 _ 2  such that the pixel electrode  82  contacts a portion of the first drain electrode portion  59 _ 1  and a portion of the second drain electrode portion  59 _ 2 . In addition, the pixel electrode  82  may be formed in a region of the gate insulating film which is exposed by the contact hole  77 . 
         [0123]    The pixel electrode  82  may be made of a transparent conductor, such as ITO or IZO, or a reflective conductor such as aluminum. 
         [0124]    Although not shown in the drawings, each color filter (not shown) may be formed in a pixel region before the passivation film  70  is formed in the pixel region. Each color filter absorbs or passes light of a predetermined wavelength by using a red, green or blue pigment included therein in order to represent red, green or blue color. The color filters may represent various colors by additively mixing red, green and blue light that passed therethrough. 
         [0125]    The second display substrate  200  will now be described below. A black matrix  220  for preventing leakage of light is formed on an insulating substrate  210 . The black matrix  220  is formed in regions other than a region facing the pixel electrode  82 , thereby defining a pixel region. 
         [0126]    The black matrix  220  may overlap the drain electrode  59  disposed on the first display substrate  100 . That is, the black matrix  220  may overlap the first drain electrode portion  59 _ 1  and the second drain electrode portion  59 _ 2  of the drain electrode  59 . In order to minimize a reduction in the aperture ratio due to the black matrix  220 , the black matrix  220  may overlap part of the first drain electrode portion  59 _ 1 . That is, a side of the first drain electrode portion  59 _ 1  which does not meet the second drain electrode portion  59 _ 2  may not be overlapped by the black matrix  220 . 
         [0127]    The black matrix  220  may overlap the contact hole  77  of the first display substrate  100 . That is, the contact hole  77  may be disposed in a region in which the black matrix  220  of the second display substrate  200  is formed. Thus, since the contact hole  77  is not disposed in a pixel region, the aperture ratio of the display device  1  can be increased. A width of the contact hole  77  may increase as the distance between the contact hole  77  and the semiconductor pattern  42  is reduced and may decrease as the distance between the contact hole  77  and the semiconductor pattern  42  increases. 
         [0128]    Specifically, referring to  FIG. 25A , when a contact hole  77   —   a  is separated from the semiconductor pattern  42  by a first gap G 1 , it may have a first aperture width W 1 . Referring to  FIG. 25B , when a contact hole  77   —   b  is separated from the semiconductor pattern  42  by a second gap G 2 , it may have a second aperture width W 2 . Here, if the second gap G 2  is wider than the first gap G 1 , the second aperture width W 2  should be narrower than the first aperture width W 1 . If the second aperture width W 2  is substantially equal to or wider than the first aperture width W 1 , a portion of the contact hole  77   —   b  may be outside the region in which the black matrix  220  is formed. Accordingly, the overall aperture ratio of the display device  1  may be reduced. Therefore, if the second gap G 2  is wider than the first gap G 1 , the second aperture width W 2  should be narrower than the first aperture width W 1 . The black matrix  220  may be made of an opaque organic material or opaque metal. 
         [0129]    Color filters (not shown) for representing colors may be formed on the insulating substrate  210 . In this case, the color filters may not be formed on the first display substrate  100 . That is, in the display device  1  according to the present invention, color filters may be formed on the first display substrate  100  or the second display substrate. 
         [0130]    An overcoat layer  230  may be formed on the black matrix  220  in order to planarize step heights of the second display substrate  200 . The overcoat layer  240  is made of a transparent organic material, protects the color filters and the black matrix  220 , and insulates the black matrix  220  and the color filters from a common electrode  240  which will be described later. 
         [0131]    The common electrode  240  is formed on the overcoat layer  230 . The common electrode  240  may be made of a transparent conductive material, such as ITO or IZO. 
         [0132]    The liquid crystal layer  300  is interposed between the first display substrate  100  and the second display substrate  200 . The voltage difference between the pixel electrode  82  and the common electrode  240  determines transmittance. 
         [0133]    A colored column spacer  501  is interposed between the first display substrate  100  and the second display substrate  200 . The colored column spacer  501  according to the fifth exemplary embodiment maintains a cell gap between the first display substrate  100  and the second display substrate  200 . The colored column spacer  501  may overlap the contact hole  77  of the first display substrate  100 . Accordingly, external light can be prevented from entering a thin-film transistor through the contact hole  77 . The colored column spacer  501  may be, e.g., black. 
         [0134]    While teachings in accordance with the present disclosure of invention have been particularly shown and described with reference to exemplary embodiments thereof, it will be understood by those of ordinary skill in the art in light of the foregoing that various changes in form and detail may be made therein without departing from the spirit and scope of the present teachings. The exemplary embodiments should be considered in a descriptive sense only and not for purposes of limitation.