Patent Document

This application is a Divisional of U.S. patent application Ser. No. 10/631,725, filed Aug. 1, 2003, now U.S. Pat. No. 7,135,360 and claims the benefit of Korean Patent Application No. 81459/2002 filed in Korea on Dec. 18, 2002, both of which are hereby incorporated by reference in their entirety. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a display device and a method of fabricating a display device, and particularly, to a liquid crystal display device and a method of fabricating a liquid crystal display device. 
     2. Description of the Related Art 
     In general, flat panel displays, such as liquid crystal display (LCD) devices, commonly include an active device, such as a thin film transistor, provided at pixel regions to drive the display device. In addition, a driving method for the LCD device is commonly referred to as an active matrix driving type method, wherein the active device is disposed at respective pixel regions that are arranged in a matrix configuration to drive corresponding pixels. 
       FIG. 1  is a plan view of an LCD device according to the related art. In  FIG. 1 , a TFT LCD uses a thin film transistor (TFT)  10  as an active device. In addition, an N×M matrix configuration of pixels are arranged along longitudinal and transverse directions, and includes the TFT  10  formed at a crossing region of a gate line  3 , which receives a scan signal supplied from a driving circuit of an exterior portion of the LCD device, and a data line  5 , which receives an image signal. The TFT comprises a gate electrode  11  connected to the gate line  3 , a semiconductor layer  12  formed on the gate electrode  11 , which is activated when the scan signal is supplied to the gate electrode  11 , and a source electrode  13  and a drain electrode  14  formed on the semiconductor layer  12 . A pixel electrode  16 , which is connected to the source and drain electrodes  13  and  14  to operate a liquid crystal material (not shown) by supplying the image signal through the source and drain electrodes  13  and  14  as the semiconductor layer  12  is activated, is formed on a display area of the pixel. 
       FIG. 2  is a cross sectional view along I-I′ of  FIG. 1  according to the related art. In  FIG. 2 , the TFT  10  is formed on a first substrate  20  made of a transparent material, such as glass, and includes the gate electrode  11  formed on the first substrate  20 , a gate insulating layer  22  deposited on an entire surface of the first substrate  20  upon which the gate electrode is formed  11 , a semiconductor layer  12  formed on the gate insulating layer  22 , source and drain electrodes  13  and  14  formed on the semiconductor layer  12 , and a passivation layer  24  deposited on an entire surface of the first substrate  20 . A pixel electrode  16 , which is connected to the drain electrode  14  of the TFT  10  through a contact hole  26  formed on the passivation layer  24 , is formed on the passivation layer  24 . 
     In addition, a black matrix  32 , which is formed on a non-display area (i.e., a TFT  10  forming area) and an area between pixels to prevent light from transmitting to the non-display area, and a color filter layer  34  for producing R(Red), G(Green), and B(Blue) colors are formed on a second substrate  30  made of transparent material, such as glass. The first and second substrates  20  and  30  are bonded together, and a liquid crystal material layer  40  is formed therebetween. 
       FIGS. 3A to 3I  are cross sectional views of a fabrication method of an LCD device according to the related art. In  FIG. 3A , a metal layer  11   a  is formed by depositing metal material on the first substrate  20 , and a photoresist layer  60   a  is formed on the metal layer  11   a  and baked at a certain temperature. Then, light is radiated onto the photoresist layer  60   a  through a mask  70 . 
     In  FIG. 3B , a developer is applied to the photoresist layer  60   a , and a photoresist pattern  60  is formed on the metal layer  11   a . For example, when the photoresist is a negative photoresist, portions of the photoresist layer  60   a  that are not exposed to the light are removed by the developer. 
     In  FIG. 3C , an etching solution is applied to the metal layer  11   a . Accordingly, a portion of the metal layer  11   a  blocked by the photoresist pattern  60  remains, whereby a gate electrode  11  is formed on the first substrate  20 . 
     In  FIG. 3D , a gate insulating layer  22  is formed on an entire surface of the first substrate  20 , and a semiconductor layer  12   a  is formed on the gate insulating layer  22 . Then, a photoresist layer is deposited onto the semiconductor layer  12   a , and a mask (not shown) is provided such that light is radiated onto the photoresist layer and developed to form a photoresist pattern  62  on the semiconductor layer  12   a . Next, an etching solution is applied to the semiconductor layer  12   a  such that only a portion of the semiconductor layer  12   a  under the photoresist pattern  62  remains on the gate insulating layer  22 . 
     In  FIG. 3E , the photoresist pattern  62  (in  FIG. 3D ) is removed. Accordingly, a semiconductor layer  12  is formed on the gate electrode  11 . 
     In  FIG. 3F , a metal material is deposited on an entire surface of the first substrate  20 , and a photoresist pattern (not shown) is formed using a mask (not shown). Then, the metal material is etched using the photoresist pattern (not shown) for forming a source electrode  13  and a drain electrode  14  on the semiconductor layer  12 . 
     In addition, a passivation layer  24  is deposited on the first substrate  20  upon which the source and drain electrodes  13  and  14  are formed to protect the TFT. Then, a portion of the passivation layer  24  overlying the drain electrode  14  is etched using a photolithographic process to form a contact hole  26  in the passivation layer  24 . 
     In  FIG. 3H , a transparent material, such as indium tin oxide (ITO), is deposited onto the passivation layer  24 , and patterned using a photolithographic process to form the pixel electrode  16  on the passivation layer  24 . Accordingly, the pixel electrode  16  is electrically connected to the drain electrode  14  through the contact hole  26  formed in the passivation layer  24 . 
     In  FIG. 3I , a black matrix  32  and a color filter layer  34  are formed on a second substrate  30 , the first and second substrates  20  and  30  are bonded together, and a liquid crystal material layer  40  is formed between the bonded first and second substrates  20  and  30 . 
     In the fabrication method of  FIGS. 3A to 3I , the source, drain, and pixel electrodes  13 ,  14 , and  16  and/or the semiconductor layer  12  is formed using photolithographic processes that use a photoresist layer. However, use of the photoresist layer in the photolithographic process is problematic. First, the fabrication processes are relatively complex. For example, the photoresist pattern is formed through processes of photoresist coating, baking, exposure, and developing. In addition, in order to bake the photoresist layer, a soft-baking process is performed at a first low temperature and a hard-baking process is performed at a second higher temperature. 
     Second, a majority of fabrication costs lie with the fabrication of active switching devices. During fabrication of the active switching devices, a plurality of photoresist patterns are required. For example, the cost of forming the photoresist patterns is about 40-45% of the total cost of fabricating the LCD device. 
     Third, the process for forming the photoresist patterns produces massive amounts of environment pollutants that must be recovered during the fabrication process of the LCD device. In general, the photoresist layer is made by spin coating a photoresist material to achieve a certain thickness. Accordingly, large amounts of the spun-off photoresist material are not used and some amounts are unfortunately released into the environment. In addition, recovery of the spun-off photoresist material increases fabrication costs. 
     Fourth, since the photoresist layer is applied using the spin coating method, it is difficult to control the thickness of the photoresist layer. Accordingly, thickness of the photoresist layer is non-uniform. Thus, during removal of portions of the non-uniform photoresist layer, residual amounts of the photoresist layer are created that negatively impact operation of the active switching devices. 
     SUMMARY OF THE INVENTION 
     Accordingly, the present invention is directed to a liquid crystal display device and method of fabricating a liquid crystal device that substantially obviates one or more of the problems due to limitations and disadvantages of the related art. 
     An object of the present invention is to provide an LCD device fabricated using a pattern forming method to simplify fabrication processes and reduce fabrication costs. 
     Another object of the present invention is to provide a method of fabricating an LCD device having simplified fabrication processes and reduced fabrication costs. 
     Additional features and advantages of the invention will be set forth in the description which follows, and in part will be apparent from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended claims. 
     To achieve these and other advantages and in accordance with the purpose of the present invention, as embodied and broadly described, a liquid crystal display device includes a plurality of gate lines and data lines on a first substrate defining a plurality of pixel regions, a thin film transistor within the pixel regions, a pixel electrode within the pixel regions, and at least one TiOx layer provided with the thin film transistor. 
     In another aspect, a liquid crystal display device includes a plurality of gate lines and data lines on a first substrate defining a plurality of pixel regions, a thin film transistor within pixel regions, a pixel electrode within the pixel regions, and a TiO 2  layer provided in at least one of the thin film transistor and an upper portion of the pixel electrode. 
     In another aspect, a liquid crystal display device includes a plurality of gate lines and data lines on a first substrate defining a plurality of pixel regions, a thin film transistor within the pixel regions, a pixel electrode within the pixel regions, and a metal layer provided in the thin film transistor. 
     In another aspect, a method of fabricating a liquid crystal display device includes forming a gate electrode on a first substrate, forming a TiOx layer on the gate electrode using a Ti masking layer, forming a gate insulating layer on the first substrate, forming a semiconductor layer on the gate insulating layer, forming source and drain electrodes on the semiconductor layer, forming a passivation layer on the first substrate, and forming a pixel electrode on the passivation layer. 
     In another aspect, a method of fabricating a liquid crystal display device includes forming a gate electrode on a first substrate, forming a TiO 2  layer on the gate electrode, forming a gate insulating layer on the first substrate, forming a semiconductor layer on the gate insulating layer, forming source and drain electrodes on the semiconductor layer, forming a passivation layer on the first substrate, and forming a pixel electrode on the passivation layer. 
     It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are intended to provide further explanation of the invention as claimed. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the principles of the invention. In the drawings: 
         FIG. 1  is a plan view of an LCD device according to the related art; 
         FIG. 2  is a cross sectional view along I-I′ of  FIG. 1  according to the related art; 
         FIGS. 3A to 3I  are cross sectional views of a fabrication method of an LCD device according to the related art; 
         FIGS. 4A to 4F  are cross sectional views of an exemplary pattern forming method for fabricating an LCD device according to the present invention; 
         FIGS. 5A to 5F  are cross sectional views of another exemplary pattern forming method for fabricating an LCD device according to the present invention; 
         FIGS. 6A to 6G  are cross sectional views of an exemplary method of fabricating an LCD device according to the present invention; and 
         FIGS. 7A to 7F  are cross sectional views of another exemplary method of fabricating an LCD device according to the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Reference will now be made in detail to the preferred embodiments of the present invention, examples of which are illustrated in the accompanying drawings. 
     In general, Ti is stable under atmospheric conditions. However, Ti is converted into TiOx when it is heated in an oxygen atmosphere. Accordingly, since Ti and TiOx have different etching selectivity ratios, TiOx may be formed by oxidizing a portion of Ti and an etching solution may be applied to remove the Ti and to form a TiOx pattern. In addition, when light of a certain wavelength is irradiated onto the TiOx, surface properties of the TiOx may become hydrophilic. Accordingly, the TiOx pattern may be formed by making use of differences between hydrophlicity and hydrophobicity. Thus, a metal layer may be precisely etched using the TiOx pattern. 
       FIGS. 4A to 4F  are cross sectional views of an exemplary pattern forming method for fabricating an LCD device according to the present invention. In  FIGS. 4A to 4F , a metal pattern may be formed to create an electrode, a semiconductor pattern, and an insulating pattern. 
     In  FIG. 4A , a metal layer  103  may be formed on an entire surface of a substrate  101  made of insulating material, such as glass or a semiconductor material. Then, a Ti layer  10  may be formed on an entire surface of the substrate  101  to overlie the metal layer  103 . The Ti layer  110  may be formed using evaporating or sputtering methods. 
     In  FIG. 4B , light, such as ultraviolet light or laser produced light, may be irradiated on an area where a metal pattern will be formed using a mask  107 . Irradiation of the light results in deposition of energy onto the Ti layer  110 . 
     In  FIG. 4C , since the irradiation of the light may be performed in an atmospheric or oxidizing atmosphere, portions of the Ti layer  110  exposed to the light may be oxidized. The oxidation of the Ti layer  110  may begin at a surface of the Ti layer  110  and may continue through an entire thickness of the Ti layer  110  over a period of time. Accordingly, the Ti layer  110  may include unexposed portions of the Ti layer  110   b  and an exposed portion of the Ti layer  110   a.    
     In  FIG. 4D , the unexposed portions of the Ti layer  110   b  may be removed to form a patterned TiOx layer  110   a . The unexposed portions of the Ti layer  110   b  may be removed using wet or dry etching processes. During the wet etching process, acids, such as HF, may be used, wherein the HF acid may not react with the TiOx layer  110   a . Accordingly, HF acid etches the Ti layer  110   b , and leaves the TiOx pattern  110   a  on the metal layer  103 . In addition, other acids besides HF may be used in order to etch the Ti material. However, it is desirable that H 2 SO 4  may not be used since H 2 SO 4  may not react with the Ti material. 
     During the dry etching process, the etching rate of the TiOx using Cl 2  gas or Cl 2  mixed gas, such as CF 4 /Cl 2 /O 2  gas, is much lower than the etching rate of the Ti. Accordingly, the Cl 2  gas or Cl 2  mixed gas may be mainly used as the etching gas. 
     In  FIG. 4D , when the metal layer  103  is etched using the wet etching process or the dry etching process, the TiOx pattern  110   a  blocks the etching solution (in case of the wet etching process) or the etching gas (in case of the dry etching process). Accordingly, portions of the metal layer  103   a  underlying the TiOx pattern  110   a  remain on the substrate  101 . 
     In  FIG. 4F , the TiOx pattern  110   a  on the metal pattern  103   a  may be etched and removed from the metal pattern  103   a . The TiOx pattern  110   a  may be etched using the wet and dry etching processes. During the wet etching process, H 2 SO 4  (SO 4  ion is reacted with the TiOx and removed) may be used, and during the dry etching process, Cl 2 /N 2  gas or CF 4 /Cl 2  gas may be used. 
       FIGS. 5A to 5F  are cross sectional views of another exemplary pattern forming method for fabricating an LCD device according to the present invention. In  FIG. 5A , a metal layer  203  may be formed by depositing metal material(s) on a substrate  201  made of insulating material(s), such as glass or semiconductor material(s). Then, TiOx, especially TiO 2 , may be deposited to form a TiO 2  layer  210  on the metal layer  203 . The TiO 2  layer  210  may be formed directly onto the metal layer  203  through evaporation or sputtering methods, or may be formed by oxidizing Ti using applications of heat and/or light after depositing the Ti onto the metal layer  203 . 
     In  FIG. 5B , light, such as ultraviolet light or laser light, may be irradiated onto a first area of the TiO 2  layer  210  using a mask  207  to form a patterned area. Accordingly, the first area of the TiO 2  layer  210  may become hydrophilic. For example, TiO 2  material is a photocatalyst material having hydrophobic properties. However, when ultraviolet light or laser light is irradiated onto the TiO 2  material, an OH group may be formed on a surface of the TiO 2  material, thereby producing a hydrophilic material. A contact angle may be defined as an angle that makes a thermodynamic balance on a surface of a solid and that may be indicative of surface wettability (i.e., hydrophilicity) of a material. Accordingly, when the ultraviolet light is irradiated onto the TiO 2  layer  210  for more than a predetermined time, such as one hour, a contact angle may be gradually reduced to near 0 (i.e., hydrophilicity). 
     In  FIG. 5C , the TiO 2  layer may be divided into a first TiO 2  layer  210   a  having a hydrophilic surface  211  and a second TiO 2  layer  210   b  having hydrophobic properties by the irradiation of the ultraviolet light or the laser light. When the H 2 SO 4  or an etching solution of alkali is applied to TiO 2  layers each having different surface properties, the OH group of the first TiO 2  layer  210   a  that has hydrophilic properties may be combined with SO 4  ions of the H 2 SO 4 . That is, the surface  211  of the first TiO 2  layer  210   a  may be protected by the OH group. Accordingly, the hydrophobic second TiO 2  layer  210   b  may be removed by the etching solution, and the first TiO 2  layer  210   a  may remain on the metal layer  203 , as shown in  FIG. 5D . 
     In  FIG. 5E , the etching solution may be applied to the metal layer  203 . Accordingly, portions of the metal layer  203  may be removed that do not underlie the first TiO 2  layer  210   a.    
     In  FIG. 5F , the first TiO 2  layer  210   a  may be removed using a gas, such as Cl 2 /N 2  or CF 4 /Cl 2 . Accordingly, a metal pattern  203   a  may be formed on the substrate  201 . 
     Using the pattern forming method according to the present invention, a pattern may be formed by making use of different etching selectivity rates of a first metal, such as Ti, and of a first metal oxide, such as TiOx, and by making use of surface properties of the first metal oxide. The pattern forming method according to the present invention is advantageous as compared to the pattern forming method according to the related art that uses photolithographic processes including photoresist materials. 
     First, in the pattern forming method according to the related art, baking processes (soft-baking and hard-baking) are required after applying the photoresist, and an ashing process is required when the photoresist is removed. However, according to the present invention, since a photoresist is not required, the fabrication process is simplified. 
     Second, in the pattern forming method according to the related art, since the photoresist processing and patterning are additional fabrication processes, expensive equipment for the photoresist processing (i.e., a spin coater) is required during each individual process step in addition to equipment for fabricating the active devices (i.e., thin film transistors). On the contrary, the pattern forming process according to the present invention uses metal and metal oxide materials that may be produced using the same equipment used to fabricate the active devices. For example, when the metal pattern is formed, the metal layer and the Ti layer, which are the objects to be etched, may be formed in a vacuum chamber using similar methods (i.e., evaporation or sputtering). Accordingly, no addition equipment, other than those used to fabricate the active devices, is required. Thus, fabrication costs may be greatly reduced as compared to costs associated with the pattern forming method according to the related art that use the photoresist material. 
     Third, introduction of environment pollutants may be reduced since large amounts of wasted photoresist material are not produced using the pattern forming method according to the present invention. In addition, fabrication costs may be reduced by not producing the large amounts of wasted photoresist material since the pattern forming method according to the present invention uses metal and metal oxide materials. 
       FIGS. 6A to 6G  are cross sectional views of an exemplary method of fabricating an LCD device according to the present invention. In  FIG. 6A , a metal layer  311   a  may be formed on a first substrate  320  made of a transparent material, such as glass, by depositing a metal, such as Al, an Al alloy, and Cu, and a metal layer  370   a , such as Ti, may be formed on the metal layer  311   a . Next, light, such as ultraviolet light or laser light, may be radiated onto the Ti layer  370   a  through a mask  380 . Accordingly, portions of the Ti layer  370   a  exposed to the light may become oxidized and converted into TiOx. 
     In  FIG. 6B , an etching solution (i.e., HF) may be applied, wherein the unexposed portions of the Ti layer  370   a  may be removed leaving a TiOx pattern  370  on the metal layer  311   a . When the etching solution is applied, the portion of metal layer  311   a  underlying the TiOx pattern  370  remains on the first substrate  320 . Accordingly, a gate electrode  311  (in  FIG. 6C ) and the TiOx pattern are formed on the first substrate  320   
     In  FIG. 6C , a gate insulating layer  322  may be formed on an entire surface of the first substrate  320  using a chemical vapor deposition (CVD) method, for example, a semiconductor layer  312   a  may be deposited onto the gate insulating layer  322 , and a Ti layer  372   a  may be formed on the semiconductor layer  312   a . Accordingly, when light, such as ultraviolet light or laser light, is radiated onto a portion of the Ti layer  372   a  using a mask  382 , portions of the Ti layer  372   a  oxidizes to become TiOx. 
     Then, when an etching solution is applied to the Ti layer  372   a , the only remaining portion of the Ti layer  372   a  is the oxidized TiOx portion, thereby forming a TiOx pattern. Next, when the semiconductor layer  312   a  is etched using etching gas, the portions of the semiconductor layer  312  underlying the TiOx pattern  372  will remain on the gate insulating layer  322 , as shown in  FIG. 6D . Accordingly, the TiOx pattern  372  may remain on the semiconductor layer  312 . Alternatively, the TiOx pattern  372  may be removed form the semiconductor layer  312 . 
     Since the semiconductor layer  312  may include silicon, the TiOx pattern  372  provided on the semiconductor layer  312  may react with the silicon to form Ti-silicide. On the other hand, since the Ti-silicide has a resistance lower than a resistance of the semiconductor layer  312 , an ohmic contact may be formed on the semiconductor layer  312  beneath subsequently formed source and drain electrodes  313  and  314  (in  FIG. 6E ). That is, the converted TiOx pattern  372  provided on the semiconductor layer  312  may remain to function as the ohmic contact layer. 
     In  FIG. 6D , a metal layer  313   a , such as Cr, Mo, Al, an Al alloy, and Cu, may be formed on an entire surface of the first substrate  320  upon which the semiconductor layer  312  may be formed, and a Ti layer  373   a  may be formed on the metal layer  313   a . Accordingly, when the metal layer  313   a  is etched using the mask  384 , the source electrode  313  and the drain electrode  314  are formed on the semiconductor layer  312 , and TiOx patterns  373  and  374  (in  FIG. 6E ) may be formed on the source and drain electrodes  313  and  314 , respectively. Alternatively, the TiOx patterns  373  and  374  may be removed from the source and drain electrodes  313  and  314 , respectively. When the metal layer  313   a  is etched, the TiOx pattern  372  formed on some areas of the semiconductor layer  312  may be removed to form a channel area of the semiconductor layer  312 . 
     Although not shown, the gate electrode  311 , the source electrode  313 , and the drain electrode  314  may be formed as a plurality of individual layers each comprising a single metal material, or may be formed as a single layer comprising a plurality of different material layers, such as alloys. 
     In  FIG. 6E , a passivation layer  324  may be deposited on an entire surface of the first substrate  320 , and a portion of the passivation layer  324  provided on the drain electrode  314  may be removed to form a contact hole  326 . Next, a transparent electrode  316   a , such as indium tin oxide (ITO), and a Ti layer  376   a  may be formed on the passivation layer  324  where the contact hole  326  has been formed, and the transparent electrode  316   a  may be etched using a mask  386  to form a pixel electrode  316  (in  FIG. 6F ). In general, since the converted TiOx layer has a low light transmittance, the TiOx layer should not exist within an area where the pixel electrode is formed. Accordingly, the TiOx layer formed on the passivation layer  324  and the pixel electrode  316  may be removed, as shown in  FIG. 6F . 
     In  FIG. 6G , a second substrate  330  may include a black matrix  332  and a color filter layer  334 . Accordingly, the first and second substrates  320  and  330  may be bonded together to form an LCD device. 
     In addition, the present invention may be used together with photolithographic processes using a photoresist layer, as well as a TiOx layer. For example, the TiOx masking layer may be used to form some patterns, and a photoresist layer may be used to form other patterns. 
       FIGS. 7A to 7F  are cross sectional views of another exemplary method of fabricating an LCD device according to the present invention. In  FIG. 7A , a metal layer  411   a  may be formed on a first substrate  420  made of transparent material, such as the glass, by depositing metal material(s), such as Al, an Al alloy, and Cu, on the first substrate  420 , and a TiO 2  layer  470   a  having hydrophobic properties may be formed on the metal layer  411   a . Then, light, such as ultraviolet light or laser light, may be radiated on an upper part of the TiO 2  layer  470   a  using a mask  480 . Accordingly, a surface portion  470  (in  FIG. 7B ) of the TiO 2  layer  470   a  may be converted to have hydrophilic properties. 
     In  FIG. 7B , when H 2 SO 4  or an alkali etching solution is applied to the TiO 2  layer  470   a  (in  FIG. 7A ), the portion of the TiO 2  layer  470   a  having hydrophobic properties may be removed. Accordingly, the surface portion  470   b  of the TiO 2  pattern  470  may remain on the metal layer  411   a.    
     In  FIG. 7C , the metal layer  411   a  may be etched using an etching solution. Accordingly, a portion of the metal layer  411   a  underlying the TiO 2  pattern  470  may remain on the first substrate  420  to form a gate electrode  411 . Alternatively, the TiO 2  pattern  470  may be removed from the gate electrode  411 . Then, a semiconductor layer  412   a  and a TiO 2  layer  472   a  may be formed on an entire surface of the first substrate  420  upon which the gate electrode  411  may be formed. Next, light may be radiated onto a portion of the TiO 2  layer  472   a  using a mask  482 . 
     Accordingly, the light radiated onto the TiO 2  layer  472   a  may convert a surface of the TiO 2  layer  472   a  into hydrophilic material. Thus, the semiconductor layer  412   a  may be etched after forming a TiO 2  layer  472  (in  FIG. 7D ) having hydrophilic properties by removing the TiO 2  layer  472   a  having hydrophobic properties similar to the processes for forming the gate electrode  411 . 
     In  FIG. 7D , the semiconductor layer  412  may be formed on the gate insulating layer  422 . Accordingly, the TiO 2  pattern  472  that remains on an upper part of the semiconductor layer  412  may react with the silicon of the semiconductor layer  412  to form Ti-silicide. Thus, an ohmic contact layer  472   b  may be formed on the semiconductor layer  412 . 
     In  FIG. 7E , a source electrode  413  and a drain electrode  414  may be formed on the semiconductor layer  412  using processes similar to those shown in  FIGS. 7A-7D , wherein TiO 2  patterns  473  and  474  may be forming on the source electrode  413  and on the drain electrode  414 . Alternatively, the TiO 2  patterns  473  and  474  may be removed from the source and drain electrodes  413  and  414 . Next, a passivation layer  424  may be deposited on an entire surface of the first substrate  420 , and a portion of the passivation layer  424  corresponding to the drain electrode  414  may be etched to form a contact hole  426 . In addition, a TiO 2  pattern  476  may be formed on the passivation layer  424 . 
     Although not shown, the gate electrode  411 , the source electrode  413 , and the drain electrode  414  may be formed as a plurality of individual layers made of a single metal material, or may be formed as a plurality of single layers each made of different alloys. 
     In  FIG. 7F , an ITO layer and TiO 2  layer may be formed on the passivation layer  424 , and the ITO layer may be etched making use the hydrophobic and hydrophilic surface properties of the TiO 2  layer to form a pixel electrode  416  and a TiO 2  pattern  478  connected to the drain electrode  414  through the contact hole  426 . 
     The TiO 2  material has a resistivity of 10 3  Ωcm and a visible ray transmittance of 85%. Thus, the TiO 2  pattern  476  formed on upper part of the passivation layer  424  and the TiO 2  pattern  478  formed on an upper part of the pixel electrode  416  may not be removed. Alternatively, the TiO 2  patterns  476  and  478  may be removed. Accordingly, adjacent pixel electrodes of neighboring pixel regions are not broken and light transmitted within the pixel regions is not blocked by the TiO 2  patterns  476  and  478 . 
     In  FIG. 7F , a second substrate  430  may include a black matrix  432  and a color filter layer  434 . Then, the first and second substrates  420  and  430  may be bonded together to form the LCD device. 
     According to the present invention, since the TiO 2  layer formed on the semiconductor layer  412  reacts with the semiconductor layer  412 , no additional ohmic contact layers, or processes for forming additional ohmic contact layers may be necessary. Moreover, since the TiO 2  patterns  476  and  478  are transparent and have a relatively high resistivity, removal of the TiO 2  patterns  476  and  478  on the upper part of the passivation layer  424  and the pixel electrode  416  may not be necessary. 
     In addition, the present invention may be used together with photolithographic processes using a photoresist layer, as well as a TiOx layer. For example, the TiOx masking layer may be used to form some patterns, and a photoresist layer may be used to form other patterns. 
     It will be apparent to those skilled in the art that various modifications and variations can be made in the liquid crystal display device and method of fabricating the liquid crystal display device of the present invention without departing from the spirit or scope of the invention. Thus, it is intended that the present invention cover the modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents.

Technology Category: 3