Patent Publication Number: US-2023163217-A1

Title: Thin-film transistor, thin-film transistor array substrate, and method for manufacturing thin-film transistor

Description:
This application claims priority to Korean Patent Application No. 10-2021-0160600, filed on Nov. 19, 2021, and all the benefits accruing therefrom under 35 U.S.C. § 119, the content of which in its entirety is herein incorporated by reference. 
     BACKGROUND 
     1. Field 
     Embodiments of the disclosure relate to a thin-film transistor, a thin-film transistor array substrate, and a method for manufacturing a thin-film transistor. 
     2. Description of Related Art 
     As information society develops, demand for a display device to display an image is increasing in various fields. For example, the display device is applied to various electronic devices such as a smart phone, a digital camera, a notebook computer, a navigation system, and a smart television. 
     The display device may include a display panel that emits light for image display and a driver that supplies signals and voltages to drive the display panel. 
     The display panel may include a pair of substrates opposite to each other, and a polarizing member or a light-emitting member disposed between the pair of substrates. 
     One of the pair of substrates included in the display panel may be a thin-film transistor array substrate including a plurality of thin-film transistors for individually driving a plurality of pixel areas arranged in a display area for implementing image display. 
     SUMMARY 
     In an display panel, a thin-film transistor array substrate may include a plurality of thin-film transistors as switching elements that are turned on based on a drive signal of a voltage greater than or equal to a threshold voltage. However, when the plurality of thin-film transistors have different threshold voltage characteristics, luminance characteristics of the plurality of pixel areas are different from each other. Thus, display quality of the display panel may be deteriorated. 
     Embodiments of the disclosure provide a thin-film transistor capable of adjusting threshold voltage characteristic thereof, a thin-film transistor array substrate including the thin-film transistor, and a method for manufacturing the thin-film transistor. 
     According to an embodiment, a thin-film transistor includes a light-shielding layer disposed on a substrate, an oxygen supply layer disposed on the light-shielding layer, where the oxygen supply layer includes a metal oxide, a buffer layer disposed on the substrate and covering the oxygen supply layer, an active layer disposed on the buffer layer, where the active layer includes a channel area overlapping the light-shielding layer, and a first electrode area and a second electrode area respectively in contact with opposing sides of the channel area, a gate insulating layer disposed on the channel area of the active layer, a gate electrode disposed on the gate insulating layer, an interlayer insulating layer disposed on the buffer layer and covering the active layer and the gate electrode, where a first electrode hole is defined through the interlayer insulating layer to overlap a portion of the first electrode area of the active layer, and a first electrode disposed on the interlayer insulating layer and connected to the first electrode area of the active layer via the first electrode hole. 
     In an embodiment, a contact hole may be defined through the interlayer insulating layer and the buffer layer to overlap a portion of the oxygen supply layer. In such an embodiment, the light-shielding layer may be connected to one of the gate electrode and the first electrode via the contact hole and the oxygen supply layer. 
     In an embodiment, a portion of the oxygen supply layer corresponding to the contact hole may have a first thickness, and another portion of the oxygen supply layer may have a second thickness smaller than the first thickness. 
     In an embodiment, the buffer layer may be disposed directly on the substrate and have a planarized top surface. In such an embodiment, a portion of the buffer layer in contact with the substrate may have a third thickness, and the third thickness of the portion of the buffer layer may exceed a sum of the first thickness of the portion of the oxygen supply layer and a thickness of the light-shielding layer. 
     In an embodiment, a difference between a depth of the first electrode hole and a depth of the contact hole may be about 300 angstrom (Å) or smaller. 
     In an embodiment, the metal oxide may include at least one selected from indium (In), gallium (Ga), zinc (Zn), tin (Sn), titanium (Ti), zirconium (Zr), and hafnium (Hf). 
     In an embodiment, the active layer may include an oxide semiconductor including at least one selected from indium (In), gallium (Ga), zinc (Zn), tin (Sn), titanium (Ti), zirconium (Zr), and hafnium (Hf). 
     In an embodiment, each of the active layer and the oxygen supply layer may include indium-gallium-zinc-oxide (“IGZO”). 
     In an embodiment, the thin-film transistor may further include an auxiliary oxygen supply layer disposed between the gate insulating layer and the gate electrode, where auxiliary oxygen supply layer may include the metal oxide. 
     In an embodiment, the thin-film transistor may further include a second electrode disposed on the interlayer insulating layer and connected to the second electrode area of the active layer via a second electrode hole defined through the interlayer insulating layer to overlap a portion of the second electrode area of the active layer. 
     According to an embodiment, a thin-film transistor array substrate includes a substrate including a display area in which a plurality of pixel areas are defined, a scan line disposed in the display area and on the substrate, and extending in a first direction, and a data line disposed in the display area and on the substrate, and extending in a second direction. In such an embodiment, each of the plurality of pixel areas includes a first thin-film transistor disposed between a first drive power line and a pixel electrode, and a second thin-film transistor disposed between a gate electrode of the first thin-film transistor and the data line, and connected to the scan line. In such an embodiment, at least one selected from the first and second thin-film transistors includes a light-shielding layer disposed on the substrate, an oxygen supply layer disposed on the light-shielding layer, an active layer disposed on a buffer layer covering the oxygen supply layer, where the active layer includes a channel area overlapping the light-shielding layer, and first and second electrode areas respectively in contact with opposing sides of the channel area, a gate insulating layer disposed on the channel area of the active layer, a gate electrode disposed on the gate insulating layer, and a first electrode disposed on an interlayer insulating layer covering the active layer and the gate electrode, where the first electrode is connected to the first electrode area of the active layer via a first electrode hole defined through the interlayer insulating layer. 
     In an embodiment, the oxygen supply layer may include a metal oxide including at least one selected from indium (In), gallium (Ga), zinc (Zn), tin (Sn), titanium (Ti), zirconium (Zr), and hafnium (Hf). 
     In an embodiment, The active layer may include an oxide semiconductor including at least one selected from indium (In), gallium (Ga), zinc (Zn), tin (Sn), titanium (Ti), zirconium (Zr), and hafnium (Hf). 
     In an embodiment, the light-shielding layer may be connected to one of the gate electrode and the first electrode via a contact hole defined through the interlayer insulating layer and the buffer layer to overlap a portion of the oxygen supply layer. 
     In an embodiment, the second electrode area of the active layer of the first thin-film transistor may be connected to the first drive power line, and the first electrode of the first thin-film transistor may be connected to the light-shielding layer via the contact hole. 
     In an embodiment, the second thin-film transistor may further include a second electrode disposed on the interlayer insulating layer and connected to the second electrode area of the active layer via a second electrode hole defined through the interlayer insulating layer to overlap a portion of the second electrode area of the active layer. In such an embodiment, a third electrode hole may be defined through the interlayer insulating layer to overlap a portion of the gate electrode. In such an embodiment, the first electrode of the second thin-film transistor may be connected to the data line, and the second electrode of the second thin-film transistor may be connected to the gate electrode of the first thin-film transistor via the third electrode hole of the first thin-film transistor. 
     In an embodiment, a third electrode hole may be defined through the interlayer insulating layer to overlap a portion of the gate electrode, and a connective pattern may be disposed on the interlayer insulating layer and connects the contact hole and the third electrode hole to each other. In such an embodiment, the gate electrode of the second thin-film transistor may be connected to the light-shielding layer of the second thin-film transistor via the third electrode hole, the contact hole, and the connective pattern. 
     In an embodiment, a portion of the oxygen supply layer corresponding to the contact hole may have a first thickness, and another portion of the oxygen supply layer may have a second thickness smaller than the first thickness. 
     In an embodiment, a portion of the buffer layer in contact with the substrate has a third thickness. In such an embodiment, the third thickness of the portion of the buffer layer may exceed a sum of the first thickness of the portion of the oxygen supply layer and a thickness of the light-shielding layer. 
     In an embodiment, a difference between a depth of the first electrode hole and a depth of the contact hole may be about 300 Å or smaller. 
     In an embodiment, at least one selected from the first and second thin-film transistors may further include an auxiliary oxygen supply layer disposed between the gate insulating layer and the gate electrode, where the auxiliary oxygen supply may include a metal oxide. 
     According to an embodiment, a method for manufacturing a thin-film transistor, includes sequentially providing a light-shielding conductive material film and a metal oxide material film on a substrate, providing an oxygen supply layer by patterning the metal oxide material film while a photoresist mask layer is disposed on the metal oxide material film, providing a light-shielding layer by patterning the light-shielding conductive material film while maintaining the photoresist mask layer, removing the photoresist mask layer, providing a buffer layer which covers the oxygen supply layer, on the substrate, providing an active layer by patterning a semiconductor material film on the buffer layer, wherein the active layer includes a channel area overlapping the light-shielding layer, and a first electrode area and a second electrode area respectively in contact with both opposing sides of the channel area, providing a gate insulating layer and a gate electrode which are stacked sequentially with each other, by patterning an insulating material film covering the active layer and a first conductive material film on the insulating material film, where the gate electrode overlaps the channel area of the active layer, providing an interlayer insulating layer which covers the active layer and the gate electrode, on the buffer layer, providing a first electrode hole and a contact hole, by patterning the interlayer insulating layer and the buffer layer, where the first electrode hole corresponds to a portion of the first electrode area of the active layer and the contact hole corresponds to a portion of the oxygen supply layer, and providing a first electrode by patterning a second conductive material film on the interlayer insulating layer, wherein the first electrode is connected to the first electrode area of the active layer via the first electrode hole. 
     In an embodiment, the photoresist mask layer may include a first mask portion having a first mask thickness, and a second mask portion having a second mask thickness smaller than the first mask thickness. In such an embodiment, the method may further include, between the providing the light-shielding layer and the removing of the photoresist mask layer, removing the second mask portion of the photoresist mask layer, and additionally patterning the oxygen supply layer based on the first mask portion of the photoresist mask layer. In such an embodiment, in the additionally patterning of the oxygen supply layer, a portion of the oxygen supply layer corresponding to the first mask portion may have a first thickness, and another portion thereof may have a second thickness smaller than the first thickness. 
     In an embodiment, the method may further include planarizing a top surface of the buffer layer after the providing the buffer layer. 
     In an embodiment, after the planarizing of the top surface of the buffer layer, a portion of the buffer layer contacting the substrate may have a third thickness. In such an embodiment, the third thickness may exceed a sum of a thickness of the light-shielding layer and the first thickness of the portion of the oxygen supply layer. 
     In an embodiment, after the planarizing of the top surface of the buffer layer, another portion of the buffer layer disposed on the oxygen supply layer may have a fourth thickness. In such an embodiment, a sum of a thickness of the active layer and the fourth thickness is about 300 Å or smaller. 
     In an embodiment, in the providing the gate insulating layer and the gate electrode, an additional metal oxide material film disposed between the insulating material film and the first conductive material film is further patterned, such that an auxiliary oxygen supply layer may be provided between the gate insulating layer and the gate electrode. 
     In an embodiment, in the providing the first electrode, the first electrode is connected to the light-shielding layer via the contact hole and the oxygen supply layer. 
     In embodiments of the invention, the thin-film transistor includes the oxygen supply layer disposed on the light-shielding layer, and the active layer disposed on the buffer layer covering the oxygen supply layer. Accordingly, the heat treatment of the oxygen supply layer may allow the active layer to receive oxygens from the oxygen supply layer, such that semiconductor characteristic of the active layer may be improved. Accordingly, the threshold voltage characteristic of the thin-film transistor may be uniform. 
     In embodiments of the invention, the thin-film transistor includes the oxygen supply layer having portions of different thicknesses and the buffer layer having a planarized top surface. Accordingly, even when the contact hole penetrating the interlayer insulating layer and the buffer layer and the electrode hole defined through the interlayer insulating layer are formed in a same etching process, damage to the active layer may be prevented because a portion of the buffer layer corresponding to the contact hole is relatively thin. As a result, the number of mask processes may be reduced while suppressing the element damage, such that the manufacturing process of the transistor may be simplified. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
       The above and other features of the disclosure will become more apparent by describing in detail embodiments thereof with reference to the attached drawings, in which: 
         FIG.  1    is a perspective view showing a display device according to an embodiment; 
         FIG.  2    is a plan view showing the display device of  FIG.  1   ; 
         FIG.  3    is a schematic cross-sectional view taken along A-A′ in  FIG.  1   ; 
         FIG.  4    is a plan view showing an embodiment of a thin-film transistor array substrate of  FIG.  3   ; 
         FIG.  5    is a block diagram showing an embodiment of a portion of a display area of the thin-film transistor array substrate of  FIG.  4   ; 
         FIG.  6    is an equivalent circuit diagram showing an embodiment of a pixel driver circuit corresponding to one pixel area in  FIG.  5   ; 
         FIG.  7    is a plan view showing an embodiment of one unit pixel in  FIG.  5   ; 
         FIG.  8    is a plan view showing first and second pixel areas of  FIG.  7    in detail; 
         FIG.  9    is a plan view showing a third pixel area of  FIG.  7    in detail; 
         FIG.  10    is a cross-sectional view taken along line I-I′ in  FIG.  8    according to an embodiment; 
         FIG.  11    is a cross-sectional view taken along line II-II′ in  FIG.  8    according to an embodiment; 
         FIG.  12    is a cross-sectional view taken along line III-III′ in  FIG.  8    according to an embodiment; 
         FIG.  13    is a cross-sectional view taken along line I-I′ in  FIG.  8    according to an alternative embodiment; 
         FIG.  14    is a cross-sectional view taken along line II-II′ in  FIG.  8    according to an alternative embodiment; 
         FIG.  15    is a cross-sectional view taken along line III-III′ in  FIG.  8    according to an alternative embodiment; 
         FIG.  16    is a cross-sectional view taken along line II-II′ in  FIG.  8    according to another alternative embodiment; 
         FIG.  17    is a cross-sectional view taken along line III-III′ in  FIG.  8    according to another alternative embodiment; 
         FIG.  18    and  FIG.  19    are flowcharts showing a method for manufacturing a thin-film transistor according to an embodiment; 
         FIG.  20   ,  FIG.  21   ,  FIG.  22   ,  FIG.  23   ,  FIG.  24   ,  FIG.  25   ,  FIG.  26   ,  FIG.  27   ,  FIG.  28   ,  FIG.  29   ,  FIG.  30   ,  FIG.  31   ,  FIG.  32   ,  FIG.  33   ,  FIG.  34    and  FIG.  35    cross-sectional views showing processes of  FIG.  18    and  FIG.  19   ; 
         FIG.  36    and  FIG.  37    are flowcharts showing a method for manufacturing a thin-film transistor according to an alternative embodiment; and 
         FIG.  38   ,  FIG.  39   ,  FIG.  40   ,  FIG.  41   ,  FIG.  42   ,  FIG.  43    and  FIG.  44    are cross-sectional views showing processes of  FIG.  36    and  FIG.  37   . 
     
    
    
     DETAILED DESCRIPTIONS 
     The invention now will be described more fully hereinafter with reference to the accompanying drawings, in which various embodiments are shown. This invention may, however, be embodied in many different forms, and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. Like reference numerals refer to like elements throughout. In the accompanying figures, the thickness of layers and regions may be exaggerated for clarity. 
     Some of the parts which are not associated with the description may not be provided in order to describe embodiments of the disclosure. 
     It will also be understood that when a layer is referred to as being “on” another layer or substrate, it can be directly on the other layer or substrate, or intervening layers may also be present. In contrast, when an element is referred to as being “directly on” another element, there may be no intervening elements present. 
     Further, the phrase “in a plan view” means when an object portion is viewed from above, and the phrase “in a schematic cross-sectional view” means when a schematic cross-section taken by vertically cutting an object portion is viewed from the side. The terms “overlap” or “overlapped” mean that a first object may be above or below or to a side of a second object, and vice versa. Additionally, the term “overlap” may include layer, stack, face or facing, extending over, covering, or partly covering or any other suitable term as would be appreciated and understood by those of ordinary skill in the art. The expression “not overlap” may include meaning such as “apart from” or “set aside from” or “offset from” and any other suitable equivalents as would be appreciated and understood by those of ordinary skill in the art. The terms “face” and “facing” may mean that a first object may directly or indirectly oppose a second object. In a case in which a third object intervenes between a first and second object, the first and second objects may be understood as being indirectly opposed to one another, although still facing each other. 
     The spatially relative terms “below,” “beneath,” “lower,” “above,” “upper,” or the like, may be used herein for ease of description to describe the relations between one element or component and another element or component 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, in the case where a device illustrated in the drawing is turned over, the device positioned “below” or “beneath” another device may be placed “above” another device. Accordingly, the illustrative term “below” may include both the lower and upper positions. The device may also be oriented in other directions and thus the spatially relative terms may be interpreted differently depending on the orientations. 
     When an element is referred to as being “connected” or “coupled” to another element, the element may be “directly connected” or “directly coupled” to another element, or “electrically connected” or “electrically coupled” to another element with one or more intervening elements interposed therebetween. It will be further understood that when the terms “comprises,” “comprising,” “has,” “have,” “having,” “includes” and/or “including” are used, they may specify the presence of stated features, integers, steps, operations, elements and/or components, but do not preclude the presence or addition of other features, integers, steps, operations, elements, components, and/or any combination thereof. 
     It will be understood that, although the terms “first,” “second,” “third,” or the like may be used herein to describe various elements, these elements should not be limited by these terms. These terms are used to distinguish one element from another element or for the convenience of description and explanation thereof. For example, when “a first element” is discussed in the description, it may be termed “a second element” or “a third element,” and “a second element” and “a third element” may be termed in a similar manner without departing from the teachings herein. 
     The terms “about” or “approximately” as used herein is inclusive of the stated value and means within an acceptable range of deviation for the particular value as determined by one of ordinary skill in the art, considering the measurement in question and the error associated with measurement of the particular quantity (for example, the limitations of the measurement system). For example, “about” may mean within one or more standard deviations, or within ±30%, 20%, 10%, 5% of the stated value. 
     In the specification and the claims, the term “and/or” is intended to include any combination of the terms “and” and “or” for the purpose of its meaning and interpretation. For example, “A and/or B” may be understood to mean “A, B, or A and B.” The terms “and” and “or” may be used in the conjunctive or disjunctive sense and may be understood to be equivalent to “and/or.” In the specification and the claims, the phrase “at least one of” is intended to include the meaning of “at least one selected from” for the purpose of its meaning and interpretation. For example, “at least one of A and B” may be understood to mean “A, B, or A and B.” 
     Unless otherwise defined or implied, all terms used herein (including technical and scientific terms) have the same meaning as commonly understood by those skilled 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 ideal or excessively formal sense unless clearly defined in the specification. 
     Embodiments are described herein with reference to cross section illustrations that are schematic illustrations of idealized embodiments. As such, variations from the shapes of the illustrations as a result, for example, of manufacturing techniques and/or tolerances, are to be expected. Thus, embodiments described herein should not be construed as limited to the particular shapes of regions as illustrated herein but are to include deviations in shapes that result, for example, from manufacturing. For example, a region illustrated or described as flat may, typically, have rough and/or nonlinear features. Moreover, sharp angles that are illustrated may be rounded. Thus, the regions illustrated in the figures are schematic in nature and their shapes are not intended to illustrate the precise shape of a region and are not intended to limit the scope of the present claims. 
     Hereinafter, embodiments of the disclosure will be described in detail with reference to the accompanying drawings. 
       FIG.  1    is a perspective view showing a display device according to an embodiment.  FIG.  2    is a plan view showing the display device of  FIG.  1   .  FIG.  3    is a schematic cross-sectional view showing an example of A-A′ in  FIG.  1   .  FIG.  4    is a plan view showing an example of a thin-film transistor array substrate of  FIG.  3   . 
     First, as used herein, “top”, and “top surface” indicate a direction or a surface in which light from a display device  1  emits, that is, a Z-axis direction. Moreover, as used herein, “bottom” and “bottom surface” refer to an opposite direction to the Z-axis direction. Further, “left”, “right”, “upper” and “lower” indicate directions of a thin-film transistor array substrate  10  in a plan view. For example, “left” indicates a direction opposite to a X-axis direction, “right” indicates the X-axis direction, “upper” indicates a Y-axis direction, and “lower” indicates an opposite direction to the Y-axis direction. 
     Referring to  FIG.  1   , an embodiment of the display device  1  displays a moving image or a still image and may be used as a display screen of each of portable electronic devices such as mobile phones, smart phones, tablet personal computer (“PC”s), smart watches, watch phones, mobile communication terminals, e-books, portable multimedia players (“PMP”), navigation devices, and ultra-mobile PCs (“UMPC”), and each of various products such as televisions, laptops, monitors, billboards, interne of things (“IOT”), etc. 
     In an embodiment, the display device  1  may be embodied as a light-emitting display device such as an organic light-emitting display device using an organic light-emitting diode, a quantum dot light-emitting display device including a quantum dot light-emitting layer, an inorganic light-emitting display device including an inorganic semiconductor, or a micro light-emitting display device using a micro or nano light emitting diode (micro or nano “LED”). Hereinafter, embodiments in which the display device  1  is embodied as the organic light-emitting display device will be described. However, the disclosure is not limited thereto. 
     Referring to  FIG.  1    and  FIG.  2   , an embodiment of the display device  1  may include the thin-film transistor array substrate  10  and a protective substrate  20  opposite to each other. 
     In an embodiment, the display device  1  may further include a display driver circuit  31  and a display circuit board  32  for driving the thin-film transistor array substrate  10 . 
     Although not shown in detail in  FIG.  1   , the display device  1  may further include a light-emitting material or a polarizing material (not shown) embedded in the thin-film transistor array substrate  10  or disposed between the thin-film transistor array substrate  10  and the protective substrate  20 . 
     In an embodiment, the display device  1  may further include an encapsulation structure for sealing a light-emitting material or a polarizing material disposed between the thin-film transistor array substrate  10  and the protective substrate  20 . 
     The thin-film transistor array substrate  10  is configured to individually activate a light- emitting material or a polarizing material corresponding to a plurality of pixel areas arranged in a display area, such that light beams from a plurality of pixel areas having respective luminance or colors may emit to an outside through the thin-film transistor array substrate  10  or the protective substrate  20 . Accordingly, the display device  1  may provide an image display function. 
     In an embodiment, the display device  1  may further include a touch sensing unit (not shown) for detecting coordinates of a point touched by a user on a display surface from which light for image display emits. 
     The touch sensing unit may be attached to one surface of the protective substrate  20 , or may be embedded between the thin-film transistor array substrate  10  and the protective substrate  20 . 
     The touch sensing unit may include a touch electrode (not shown) arranged in a touch sensing area corresponding to the display surface and include or formed of a transparent conductive material. 
     The touch sensing unit may periodically sense change in a capacitance value of the touch electrode while applying a touch drive signal to the touch electrode to detect whether a touch is input thereto, and the coordinates of a point where the touch is input. 
     The display surface of the display device  1  may have a rectangular shape having a short-side extending in the first direction (X-axis direction) and a long-side extending in the second direction (Y-axis direction) intersecting the first direction (X-axis direction). However, this is only an example. Alternatively, the display surface of the display device  1  may be implemented in various forms. 
     In an embodiment, for example, the display surface may have a shape in which a corner where the short-side extending in the first direction (X-axis direction) and the long-side extending in the second direction (Y-axis direction) meet each other is rounded to have a predefined curvature. Alternatively, the display surface may be in a form of a polygon, a circle, an oval, or the like. 
       FIG.  1    shows that the thin-film transistor array substrate  10  is in a form of a flat plate. However, the disclosure is not limited thereto. That is, the thin-film transistor array substrate  10  may have a shape in which both opposing ends in the Y-axis direction are bent. Alternatively, the thin-film transistor array substrate  10  may be flexible to be able to bend, fold, or roll. 
     The protective substrate  20  may be bonded to the thin-film transistor array substrate  10 . 
     The protective substrate  20  may provide rigidity to protect against external physical and electrical shocks. The protective substrate  20  may include or be formed of a transparent material having insulating properties and rigidity. 
     The display driver circuit  31  outputs signals and voltages for driving the thin-film transistor array substrate  10 . 
     In an embodiment, for example, the display driver circuit  31  may supply a data signal to a data line (DL in  FIG.  4   ) of the thin-film transistor array substrate  10 , and may supply first drive power to a first drive power line (VDL of  FIG.  4   ) of the thin-film transistor array substrate  10 . In an embodiment, the display driver circuit  31  may supply a scan control signal to a scan driver ( 33  in  FIG.  4   ) built in the thin-film transistor array substrate  10 . 
     The display driver circuit  31  may be embodied as an integrated circuit (“IC”). 
     An IC chip of the display driver circuit  31  may be directly mounted on the thin-film transistor array substrate  10  using a chip on glass (“COG”) scheme, a chip on plastic (“COP”) scheme, or an ultrasonic bonding scheme. In an embodiment, as shown in  FIG.  2   , the IC chip of the display driver circuit  31  may be disposed in an area of the thin-film transistor array substrate  10  not covered with the protective substrate  20 . 
     Alternatively, the IC chip of the display driver circuit  31  may be mounted on the display circuit board  32 . 
     The display circuit board  32  may include an anisotropic conductive film. The display circuit board  32  may be embodied as a flexible film such as a flexible printed circuit board, a printed circuit board or a chip on film. 
     The display circuit board  32  may be attached to electrode pads of the thin-film transistor array substrate  10 . Accordingly, lead lines of the display circuit board  32  may be electrically connected to electrode pads of the thin-film transistor array substrate  10 . 
     Referring to  FIG.  3   , when the display device  1  is embodied as an organic light-emitting display device, the thin-film transistor array substrate  10  may include a substrate  11  having a display area (DA of  FIG.  4   ), a circuit array  12  disposed on the substrate  11  and including a plurality of thin-film transistors (T 1 , T 2  and T 3  of  FIG.  6   ), and a light-emitting array  13  disposed on the circuit array  12  and including a plurality of light-emitting elements (EMD in  FIG.  6   ). 
     The display device  1  may further include a sealing layer  30  disposed at an edge and between the thin-film transistor array substrate  10  and the protective substrate  20  for bonding the thin-film transistor array substrate  10  and the protective substrate  20  to each other. 
     In an embodiment, the display device  1  may further include a filling layer (not shown) filling a gap between the thin-film transistor array substrate  10  and the protective substrate  20 . 
     Referring to  FIG.  4   , the thin-film transistor array substrate  10  has the display area DA that emits light for image display, and a non-display area NDA surrounding the display area DA. The non-display area NDA may refer to an area from an outer edge of the display area DA to an outer edge of the substrate ( 11  in  FIG.  3   ). 
     The thin-film transistor array substrate  10  includes a plurality of pixel areas PX arranged in a matrix along vertical and horizontal directions in the display area DA. Each of the plurality of pixel areas PX may be a unit area for displaying individual luminance. 
     The non-display area NDA may include a display electrode pad area DPA disposed adjacent to the edge of the substrate  11 . The thin-film transistor array substrate  10  may further include a display electrode pad DP disposed in the display electrode pad area DPA of the non-display area NDA. 
     The display circuit board ( 32  in  FIG.  1    and  FIG.  2   ) may be attached to the display electrode pad area DPA of the thin-film transistor array substrate  10  and may be electrically connected to the display electrode pad DP. 
     The thin-film transistor array substrate  10  further includes lines disposed on the display area DA for supplying a signal or power to the plurality of pixel areas PX. The lines of the thin-film transistor array substrate  10  may include the scan line SL, the data line DL, and the first drive power line VDL. 
     The scan line SL may extend in a horizontal or left-right direction (X direction). 
     The data line DL may extend in a vertical or upper-lower direction (Y direction). 
     The first drive power line VDL may extend in at least one of the left-right direction (X direction) and the upper-lower direction (Y direction). In an embodiment, for example, the first drive power line VDL may extend in the upper-lower direction (Y direction) as the data line DL extends. 
     The scan line SL supplies a scan signal for selecting a pixel area to which a data signal is to be written to pixel areas arranged in in the left-right direction (X direction). 
     The scan line SL may be connected to a scan driver  33  disposed in a portion of the non-display area NDA of the thin-film transistor array substrate  10 . 
     The scan driver  33  may receive a scan control signal from the display driver circuit  31  via at least one scan control line SCL. 
     The scan driver  33  may sequentially supply the scan signal to a plurality of scan lines SL arranged in the display area DA for each frame period for image display, based on the scan control signal. 
     According to an embodiment, as illustration of  FIG.  4   , the scan driver  33  is disposed in a portion of the non-display area NDA adjacent to a left side of the display area DA. However, this is only an example. Alternatively, the scan driver  33  may be disposed in another portion of the non-display area NDA adjacent to a right side of the display area DA. Alternatively, the scan driver  33  may be respectively disposed on both opposing sides in the left-right direction of the display area DA. 
     The data line DL is connected to pixel areas arranged in the upper-lower direction (Y direction) and supplies a data signal corresponding to luminance of each pixel area. 
     The data line DL may be connected to the display driver circuit  31 , and the display driver circuit  31  may supply a data signal of each of the pixel areas to which the scan signal is supplied to the data line DL. 
     The display driver circuit  31  may be connected to the display electrode pad DP via a data link line DLL and may receive digital video data and timing signals from the display circuit board  32  connected to the display electrode pad DP. 
     The first drive power line VDL supplies the first drive power to drive the light-emitting element (EMD in  FIG.  6   ). 
     The first drive power line VDL may receive the first drive power from the display driver circuit  31  or the display circuit board  32 . 
     Each of the plurality of pixel areas PX includes a pixel driver circuit that supplies a driving current to the light-emitting element EMD based on the power and the signals supplied thereto via the scan line SL, the data line DL and the first drive power line VDL, etc. The pixel driver circuit will be described later with reference to  FIG.  6   . 
       FIG.  5    is a block diagram showing an embodiment of a portion of the display area of the thin-film transistor array substrate of  FIG.  4   . 
     Referring to  FIG.  5   , in the display area DA of the thin-film transistor array substrate  10 , a plurality of pixel areas PX PX 1 , PX 2 , and PX 3  are arranged side by side. 
     In order for the display device  1  to display a color image, each of the plurality of pixel areas PX may correspond to one of two or more different colors. 
     In an embodiment, for example, each of the plurality of pixel areas PX may emit light of one of red R, green G, and blue B. That is, the plurality of pixel areas PX may include a first pixel area PX 1  corresponding to red R, a second pixel area PX 2  corresponding to green G, and a third pixel area PX 3  corresponding to blue B. 
     Alternatively, the plurality of pixel areas PX may emit light of one of red, green, blue, and white. 
     A unit pixel UP which is composed of or defined by a combination of two or more pixel areas of the plurality of pixel areas PX adjacent to each other and emitting different colors and acts as a unit for displaying various colors including white may be implemented. 
     In an embodiment where the unit pixels UP are arranged side by side, pixel areas corresponding to different colors are arranged adjacent to each other. That is, pixel areas of different colors are alternately arranged in the left-right direction or the upper-lower direction of the display area DA. 
     In an embodiment, for example, the display area DA may include a first vertical line in which the first pixel area PX 1  and the second pixel area PX 2  are alternately arranged with each other in the upper-lower direction, and a second vertical line in which the third pixel areas PX 3  are arranged side by side in the upper-lower direction. The first and second vertical lines may be alternately arranged with each other in the horizontal direction. 
     In an embodiment, the third pixel area PX 3  may have a width larger than that of each of the first pixel area PX 1  and the second pixel area PX 2  because luminance of blue light may not be easily controlled, compared to that of each of red light and green light. In an embodiment, for example, the width of the third pixel area PX 3  may correspond to a sum of the width of the first pixel area PX 1  and the width of the second pixel area PX 2 . 
     In an embodiment, one unit pixel UP may be implemented as a combination of the first pixel area PX 1  and the second pixel area PX 2  adjacent to each other in the upper-lower direction, and the third pixel area PX 3  adjacent thereto in the left-right direction. 
     However, an arrangement form of the pixel areas as shown in  FIG.  5    is only an example. The disclosure may include a plurality of pixel areas arranged in a different manner from that of  FIG.  5   . 
     Referring to  FIG.  5   , the scan line SL may be disposed at one side (an upper side of  FIG.  5   ) in the upper-lower direction of the unit pixel UP. 
     The first pixel area PX 1 , the second pixel area PX 2 , and the third pixel area PX 3  included in the unit pixel UP may be connected to the same scan line SL. 
     In an embodiment, the data line DL of the thin-film transistor array substrate  10  may include a first data line RDL connected to the first pixel area PX 1  corresponding to red R, a second data line GDL connected to the second pixel area PX 2  corresponding to green G, and a third data line BDL connected to the third pixel area PX 3  corresponding to blue B. 
     In an embodiment, the display area DA of the thin-film transistor array substrate  10  may further include a global control line GCL for supplying a global control signal to the plurality of pixel areas PX. The global control signal may be configured for collectively controlling supply of the power supply to the display area DA. 
     The global control line GCL may be disposed at the other side (at a lower side of  FIG.  5   ) in the upper-lower direction of the unit pixel UP. In an embodiment, although not shown in  FIG.  5   , the thin-film transistor array substrate  10  may further include an auxiliary global control line (GCL′ in  FIG.  7   ) connected to the global control line GCL and extending in a vertical direction, in an adapted manner to a structure in which the first pixel area PX 1  and the second pixel area PX 2  are alternately arranged with each other in the upper-lower direction. 
     In such an embodiment, each unit pixel UP may be connected to the first data line RDL, the second data line GDL, and the third data line BDL, the first drive power line VDL, the scan line SL, and the global control line GCL. 
     In an embodiment, for example, the first drive power line VDL may be disposed at each of both opposing sides in the left-right direction of each unit pixel UP. The first data line RDL, the second data line GDL, and the third data line BDL may be spaced apart from the first drive power line VDL. That is, the first data line RDL, the second data line GDL, and the third data line BDL may be arranged side by side in the horizontal direction and disposed between the vertical lines within each unit pixel UP, that is, between the first vertical line in which the first pixel area PX 1  and the second pixel area PX 2  are arranged with each other and the second vertical line in which the third pixel areas PX 3  are arranged with each other. The scan line SL may be disposed at one side in the vertical direction of each unit pixel UP. 
     In such an embodiment, the first data line RDL and the second data line GDL may be disposed adjacent to the first vertical line, and the third data line BDL may be disposed adjacent to the second vertical line. 
     In an embodiment, the first drive power line VDL may be shared by the vertical lines disposed around the first drive power line VDL. 
       FIG.  6    is an equivalent circuit diagram showing an embodiment of a pixel driver circuit corresponding to one pixel area in  FIG.  5   . 
     Referring to  FIG.  6   , each pixel area (PX in  FIG.  4    and  FIG.  5   ) may include a light-emitting element EMD, a first thin-film transistor T 1 , a second thin-film transistor T 2 , a third thin-film transistor T 3 , and a storage capacitor CST. 
     In an embodiment, the light-emitting element EMD may be embodied as an organic light-emitting diode including a light-emitting layer including or formed of an organic light-emitting material. Alternatively, the light-emitting element EMD may include a light-emitting layer formed of a photoelectric conversion material. 
     The first thin-film transistor T 1  is connected in series with the light-emitting element EMD while being connected between a first drive power line VDL and a second drive power line VSL. The second drive power line VSL may be a line for supplying second drive power at a lower voltage level than that of the first drive power which the first drive power line VSL supplies. 
     In an embodiment, an anode electrode of the light-emitting element EMD may be connected to a drain electrode of the first thin-film transistor T 1 , and a cathode electrode of the light-emitting element EMD may be connected to the second drive power line VSL. 
     In an embodiment, a source electrode of the first thin-film transistor T 1  may be connected to the first drive power line VDL. 
     However, a connection node between the source electrode and the drain electrode may have a configuration varying according to a structure type of the first thin-film transistor T 1 . 
     The storage capacitor CST is disposed between a first node ND 1  and a second node ND 2 . The first node ND 1  refers to a contact point connected to a gate electrode of the first thin-film transistor T 1 . The second node ND 2  refers to a contact point between the first thin-film transistor T 1  and the light-emitting element EMD. 
     The second thin-film transistor T 2  is connected to and disposed between the data line DL and the first node ND 1  and is turned on based on the scan signal of the scan line SL. When the second thin-film transistor T 2  is turned on based on the scan signal of the scan line SL, the data signal of the data line DL is supplied to the storage capacitor CST and the gate electrode of the first thin-film transistor T 1  via the second thin-film transistor T 2  and the first node ND 1 . 
     The third thin-film transistor T 3  is connected to and disposed between the first drive power line VDL and a third node ND 3 , and is turned on based on the global control signal of the global control line GCL. The third node ND 3  refers to a contact point between the source electrode of the first thin-film transistor T 1  and the third thin-film transistor T 3 . 
     When the third thin-film transistor T 3  is turned on based on the global control signal of the global control line GCL, the first drive power of the first drive power line VDL is supplied to the third node ND 3 . 
     In an embodiment, the first thin-film transistor T 1  generates a drive current corresponding to a voltage difference between a voltage of the source electrode and a voltage of the gate electrode, that is, a voltage difference between a voltage of the first node ND 1  and a voltage of the third node ND 3 , between the first drive power line VDL and between the second drive power line VSL. In such an embodiment, the light-emitting element EMD emits light of luminance corresponding to the driving current generated by the first thin-film transistor T 1 . 
     In an embodiment, as shown in  FIG.  6   , the first thin-film transistor T 1  may further include an auxiliary gate electrode connected to the second node ND 2  to form a stable channel. 
     The second thin-film transistor T 2  may further include an auxiliary gate electrode connected to the scan line SL to form a stable channel. 
     The third thin-film transistor T 3  may further include an auxiliary gate electrode connected to the global control line GCL to form a stable channel. 
     In an embodiment, for example, as shown in  FIG.  6   , the pixel driver circuit of each of the plurality of pixel areas PX has a three-transistor-one-capacitor (“3T1C”) structure including the first thin-film transistor T 1 , the second thin-film transistor T 2  and the third thin-film transistor T 3 . However, this is only an example. That is, the pixel driver circuit is not limited to 3T1C structure, and may have various structures including a 2T1C structure that does not include the third thin-film transistor T 3 . 
       FIG.  6    shows an embodiment where each of the first thin-film transistor T 1 , the second thin-film transistor T 2  and the third thin-film transistor T 3  is embodied as a metal oxide semiconductor field effect transistor (“MOSFET”). However, this is only an example. In an embodiment, at least one selected from the first thin-film transistor T 1 , the second thin-film transistor T 2 , and the third thin-film transistor T 3  may be embodied as a P-type MOSFET. 
       FIG.  7    is a plan view showing an embodiment of one unit pixel in  FIG.  5   .  FIG.  8    is a plan view showing first and second pixel areas of  FIG.  7    in detail.  FIG.  9    is a plan view showing a third pixel area of  FIG.  7    in detail. 
     Referring to  FIG.  7   , in an embodiment, the unit pixel UP may be composed of or defined by a combination of a first pixel area PX 1  corresponding to a first color, a second pixel area PX 2  corresponding to a second color, and a third pixel area PX 3  corresponding to the third color. In an embodiment, for example, the first color, the second color and the third color may be red, green and blue, respectively. 
     Because high luminance of blue is not easily controlled compared to that of each of red and green, the third pixel area PX 3  corresponding to blue may have a larger width than that of each of the first pixel area PX 1  corresponding to red and the second pixel area PX 2  corresponding to green. 
     In an embodiment, where the first pixel area PX 1  and the second pixel area PX 2  are alternately arranged with each other in the upper-lower direction, and the third pixel area PX 3  is arranged adjacent to the first pixel area PX 1  and the second pixel area PX 2  in the horizontal direction, a length in a vertical direction of the third pixel area PX 3  may correspond to a sum of lengths in the vertical direction of the first pixel area PX 1  and the second pixel area PX 2 . 
     The thin-film transistor array substrate  10  may include the global control line GCL extending in the horizontal direction and the auxiliary global control line GCL′ extending in the vertical direction. 
     The auxiliary global control line GCL′ may extend in parallel to the first drive power line VDL. 
     In an embodiment where the scan line SL is disposed at one side (a lower side of  FIG.  7   ) in the vertical direction of the unit pixel UP, the global control line GCL may be disposed at the other side (an upper side of  FIG.  7   ) in the vertical direction of the unit pixel UP. The scan line SL and the global control line GCL of a corresponding unit pixel may be disposed adjacent to a global control line GCL and a scan line SL of a unit pixel adjacent thereto in the vertical direction, respectively. 
     In an embodiment, as shown in  FIG.  6   , each of the first pixel area PX 1  and the second pixel area PX 2  may include the first thin-film transistor T 1  connected to the light-emitting element EMD, the second thin-film transistor T 2  connected to the data line DL, the scan line SL and the first thin-film transistor T 1 , and the third thin-film transistor T 3  connected to the first drive power line VDL, the global control line GCL, and the first thin-film transistor T 1 . 
     Referring to  FIG.  8   , the first thin-film transistor T 1  may be disposed between the second thin-film transistor T 2  and the third thin-film transistor T 3 . 
     The second thin-film transistor T 2  may be disposed adjacent to an intersection between the scan line SL and the data line RDL and GDL. 
     The third thin-film transistor T 3  may be disposed adjacent to the intersection point between the global control line GCL extending in the horizontal direction and the first drive power line VDL. 
     Each of the first thin-film transistor T 1 , the second thin-film transistor T 2  and the third thin-film transistor T 3  may include a light-shielding layer LSL 1 , LSL 2 , or LSL 3 , an active layer ACT 1 , ACT 2 , or ACT 3 , a gate electrode GE 1 , GE 2 , or GE 3 , a source electrode SE 2  or SE 3  and a drain electrode DE 1  and DE 2 . 
     In such an embodiment, the third node ND 3  at which the source electrode of the first thin-film transistor T 1  and the drain electrode of the third thin-film transistor T 3  are connected to each other may be implemented via connection between the active layer ACT 1  of the first thin-film transistor T 1  and the active layer ACT 3  of the third thin-film transistor T 3 . In such an embodiment, a pattern corresponding to the source electrode of the first thin-film transistor T 1  and the drain electrode of the third thin-film transistor T 3  may not be separately defined. 
     The gate electrode GE 2  of the second thin-film transistor T 2  of the first pixel area PX 1  may be composed of or defined by a portion of a pattern branched from the scan line SL in the upper-lower direction. 
     The active layer ACT 2  of the second thin-film transistor T 2  of the first pixel area PX 1  may be composed of or defined by a pattern which intersects the gate electrode GE 2  of the second thin-film transistor T 2  and whose one side overlaps the first data line RDL. 
     The source electrode SE 2  of the second thin-film transistor T 2  of the first pixel area PX 1  may be composed of or defined by a pattern which branches in the left-right direction from the first data line RDL and overlaps one side of the active layer ACT 2  of the second thin-film transistor T 2 . 
     The second thin-film transistor T 2  may further include a source electrode hole EH 21  disposed in an overlapping area between source electrode SE 2  of the second thin-film transistor T 2  and active layer ACT 2  of the second thin-film transistor T 2 . The source electrode SE 2  of the second thin-film transistor T 2  may be connected to one side of the active layer ACT 2  of the second thin-film transistor T 2  via the source electrode hole EH 21  of the second thin-film transistor T 2 . 
     The drain electrode DE 2  of the second thin-film transistor T 2  of the first pixel area PX 1  may be composed of or defined by a pattern overlapping the other side of the active layer ACT 2  of the second thin-film transistor T 2 . 
     The second thin-film transistor T 2  may further include a drain electrode hole EH 22  disposed in an overlapping area between the drain electrode DE 2  of the second thin-film transistor T 2  and the active layer ACT 2  of the second thin-film transistor T 2 . The drain electrode DE 2  of the second thin-film transistor T 2  may be connected to the other side of the active layer ACT 2  of the second thin-film transistor T 2  via the drain electrode hole EH 22  of the second thin-film transistor T 2 . 
     The light-shielding layer LSL 2  of the second thin-film transistor T 2  of the first pixel area PX 1  may be composed of or defined by a pattern partially overlapping with the gate electrode GE 2  of the second thin-film transistor T 2 . 
     In an embodiment, a gate electrode hole EH 23  corresponding to (e.g., overlapping) a portion of the gate electrode GE 2  of the second thin-film transistor T 2 , a contact hole CH 2  corresponding to a portion of a light-shielding layer LSL 2  of the second thin-film transistor T 2 , and a connective pattern CNP connecting the gate electrode hole EH 23  of the second thin-film transistor T 2  and the contact hole CH 2  of the second thin-film transistor T 2  to each other may be defined in the second thin-film transistor T 2 . 
     The light-shielding layer LSL 2  of the second thin-film transistor T 2  may be connected to the gate electrode GE 2  of the second thin-film transistor T 2  via the gate electrode hole EH 23  of the second thin-film transistor T 2 , the contact hole CH 2  of the second thin-film transistor T 2 , and the connective pattern CNP. 
     The global control line GCL extending in the horizontal direction may be connected to the global control line GCL′ extending in the vertical direction via a line hole LH. 
     The gate electrode GE 3  of the third thin-film transistor T 3  of the first pixel area PX 1  may be composed of or defined by a portion having a pattern branching from the global control line GCL in the upper-lower direction. 
     The active layer ACT 3  of the third thin-film transistor T 3  of the first pixel area PX 1  may be composed of or defined by a pattern which intersects the gate electrode GE 3  of the third thin-film transistor T 3  and whose one side overlaps the first drive power line VDL. 
     The source electrode SE 3  of the third thin-film transistor T 3  of the first pixel area PX 1  may be composed of or defined by portion of the first drive power line VDL overlapping the active layer ACT 3  of the third thin-film transistor T 3 . 
     The third thin-film transistor T 3  may further include a source electrode hole EH 31  disposed in an overlapping area between the source electrode SE 3  of the third thin-film transistor T 3  and the active layer ACT 3  of the third thin-film transistor T 3 . The source electrode SE 3  of the third thin-film transistor T 3  may be connected to one side of the active layer ACT 3  of the third thin-film transistor T 3  via the source electrode hole EH 31  of the third thin-film transistor T 3 . 
     The drain electrode (not shown) of the third thin-film transistor T 3  of the first pixel area PX 1  corresponds to the third node ND 3 . The third node ND 3  may be implemented via connection between the active layer ACT 3  of the third thin-film transistor T 3  and the active layer ACT 1  of the first thin-film transistor T 1 . Thus, the drain electrode (not shown) of the third thin-film transistor T 3  may not be separately provided. 
     The light-shielding layer LSL 3  of the third thin-film transistor T 3  of the first pixel area PX 1  may be composed of a pattern partially overlapping with the gate electrode GE 3  of the third thin-film transistor T 3 . 
     The light-shielding layer LSL 3  of the third thin-film transistor T 3  of the first pixel area PX 1  may partially overlap with a pattern branching in the horizontal direction from the auxiliary global control line GCL′. 
     In an embodiment, a contact hole CH 3  corresponding to an overlapping area between the pattern branching in the horizontal direction from the auxiliary global control line GCL′ and the light-shielding layer LSL 3  of the third thin-film transistor T 3  may be defined in the third thin-film transistor T 3 . 
     The light-shielding layer LSL 3  of the third thin-film transistor T 3  may be connected to the auxiliary global control line GCL′ via the contact hole CH 3  of the third thin- film transistor T 3 . Accordingly, both the light-shielding layer LSL 3  and the gate electrode GE 3  of the third thin-film transistor T 3  are connected to the global control line GCL. 
     The gate electrode GE 1  of the first thin-film transistor T 1  of the first pixel area PX 1  may be composed of or defined by a pattern whose one end overlaps a portion of the drain electrode DE 2  of the second thin-film transistor T 2 . 
     The other end of the gate electrode GE 1  of the first thin-film transistor T 1  may extend to an extent, e.g., as large as possible, within an effective area of the first pixel area PX 1  not to be in contact with the gate electrodes GE 2  and GE 3  of the second and third thin-film transistors T 2  and T 3 , and not to overlap the light-shielding layers LSL 2  and LSL 3  and the active layers ACT 2  and ACT 3  of the second and third thin-film transistors T 2  and T 3 . The other end of the gate electrode GE 1  of the first thin-film transistor T 1  may act as a lower electrode CBE (Capacitor Bottom Electrode) the storage capacitor (CST in  FIG.  6   ). 
     Although not shown in  FIG.  8   , the thin-film transistor array substrate  10  may further include an upper electrode (not shown) of the storage capacitor CST disposed in a layer different from a layer of the lower electrode CBE, the source electrode SE 2  and SE 3 , and the drain electrode DE 1  and DE 2 , and overlapping the lower electrode CBE. 
     In an embodiment, a gate electrode hole EH 13  corresponding to a portion of an overlapping area between the gate electrode GE 1  of the first thin-film transistor T 1  and the drain electrode DE 2  of the second thin-film transistor T 2  may be defined in the first thin-film transistor T 1 . 
     The gate electrode GE 1  of the first thin-film transistor T 1  may be connected to the drain electrode DE 2  of the second thin-film transistor T 2  via the gate electrode hole EH 13 . 
     The active layer ACT 1  of the first thin-film transistor T 1  may be composed of or defined by a pattern which intersects the gate electrode GE 1  of the first thin-film transistor T 1  and one side of which contacts the active layer ACT 3  of the third thin-film transistor T 3 . 
     The third node ND 3  may be implemented via the connection between the active layer ACT 1  of the first thin-film transistor T 1  and the active layer ACT 3  of the third thin-film transistor T 3 . Accordingly, the source electrode (not shown) of the first thin-film transistor T 1  may be excluded. 
     The drain electrode DE 1  of the first thin-film transistor T 1  may be composed of or defined by a pattern overlapping the other side of the active layer ACT 1  of the first thin-film transistor T 1 . 
     A portion of the drain electrode DE 1  of the first thin-film transistor T 1  may overlap the other side of the active layer ACT 1  of the first thin-film transistor T 1 . Another portion of the drain electrode DE 1  of the first thin-film transistor T 1  may overlap the light-shielding layer LSL 1  of the first thin-film transistor T 1 . Still another portion thereof may overlap the gate electrode GE 1  of the first thin-film transistor T 1 , that is, the lower electrode CBE. 
     In an embodiment, a drain electrode hole EH 12  disposed in the overlapping area between the drain electrode DE 1  of the first thin-film transistor T 1  and the active layer ACT 1  of the first thin-film transistor T 1 , and a contact hole CH 1  disposed in an overlapping area between the drain electrode DE 1  of the first thin-film transistor T 1  and the light-shielding layer LSL 1  of the first thin-film transistor T 1  may be defined in the first thin-film transistor T 1 . 
     The drain electrode DE 1  of the first thin-film transistor T 1  may be connected to the other side of the active layer ACT 1  of the first thin-film transistor T 1  via the drain electrode hole EH 12  of the first thin-film transistor T 1 . 
     In an embodiment, a capacitor hole CSTH for connecting the drain electrode DE 1  of the first thin-film transistor T 1  and the upper electrode (not shown) of the storage capacitor CST to each other, and a pixel hole PH for connecting the drain electrode DE 1  of the first thin-film transistor T 1  and the anode electrode of the EMD of the light-emitting element (EMD in  FIG.  6   ) to each other may be further defined in the first thin-film transistor T 1 . The capacitor hole CSTH and the pixel hole PH may overlap the drain electrode DE 1  of the first thin-film transistor T 1  and may be spaced apart from each other. 
     The light-shielding layer LSL 1  of the first thin-film transistor T 1  may be composed of or defined by a pattern including a portion overlapping both the gate electrode GE 1  of the first thin-film transistor T 1  and the active layer ACT 1  of the first thin-film transistor T 1 . 
     The light-shielding layer LSL 1  of the first thin-film transistor T 1  may be connected to the drain electrode DE 1  of the first thin-film transistor T 1  via the contact hole CH 1  of the first thin-film transistor T 1 . 
     The second pixel area PX 2  may be disposed adjacent to the first pixel area PX 1  in the vertical direction. 
     The first, second and third thin-film transistors T 1 , T 2 , and T 3  of the second pixel area PX 2  are respectively substantially to the same as the first, second and third thin-film transistors T 1 , T 2 , and T 3  of the first pixel area PX 1  except that the source electrode SE 2  of the second thin-film transistor T 2  is composed of or defined by a pattern branching from the second data line GDR, and the gate electrode GE 3  of the third thin-film transistor T 3  is composed of or defined by a pattern branching in the horizontal direction from the auxiliary global control line GCL′ extending in the vertical direction. Therefore, any repetitive detailed descriptions thereof will be omitted. 
     Referring to  FIG.  7   , the third pixel area PX 3  may be disposed adjacent to one side in the left-right direction of each of the first pixel area PX 1  and the second pixel area PX 2 . 
     Referring to  FIG.  9   , the first, second and third thin-film transistors T 1 , T 2 , and T 3  of the third pixel area PX 3  are respectively substantially to the same as the first, second and third thin-film transistors T 1 , T 2 , and T 3  of the first pixel area PX 1  except that the source electrode SE 2  of the second thin-film transistor T 2  is composed of or defined by a pattern branching from the third data line BDR. Therefore, any repetitive detailed descriptions thereof will be omitted. 
     Next, various embodiments of a thin-film transistor will be described. 
       FIG.  10    is a cross-sectional view taken along line I-I′ in  FIG.  8    according to an embodiment.  FIG.  11    is a cross-sectional view taken along line II-II′ in  FIG.  8    according to an embodiment.  FIG.  12    is a cross-sectional view taken along line III-III′ in  FIG.  8    according to an embodiment. 
     Referring to  FIG.  10   , in an embodiment, at least one selected from the first thin-film transistor T 1 , the second thin-film transistor T 2 , and the third thin-film transistor T 3  disposed in each of the pixel areas PX of a circuit array  12 A of the thin-film transistor array substrate includes a light-shielding layer (LSL 1 , LSL 2 , and LSL 3  in  FIG.  8    and  FIG.  9   ) disposed on the substrate  11 , an oxygen supply layer OSL including or formed of a metal oxide and disposed on the light-shielding layer (LSL 1 , LSL 2 , and LSL 3  in  FIG.  8    and  FIG.  9   ), a buffer layer  121  disposed on the substrate  11  and covering the oxygen supply layer OSL, an active layer (ACT 1 , ACT 2 , and ACT 3  of  FIG.  8    and  FIG.  9   ) disposed on the buffer layer  121  and including a channel area CA overlapping the light-shielding layer (LSL 1 , LSL 2 , and LSL 3  in  FIG.  8    and  FIG.  9   ), and first and second electrode areas SDA 1  and SDA 2  in contact with both opposing sides of the channel area CA, respectively, a gate insulating layer  122  disposed on the active layer (ACT 1 , ACT 2 , and ACT 3  of  FIG.  8    and  FIG.  9   ) and in the channel area CA, a gate electrode (GE 1 , GE 2 , and GE 3  in  FIG.  8    and  FIG.  9   ) disposed on the gate insulating layer  122 , an interlayer insulating layer  123  disposed on the buffer layer  121  and covering the active layer (ACT 1 , ACT 2 , and ACT 3  of  FIG.  8    and  FIG.  9   ) and the gate electrode (GE 1 , GE 2 , and GE 3  of  FIG.  8    and  FIG.  9   ), and a first electrode (DE 1 , SE 2 , DE 2 , and SE 3  of  FIG.  8    and  FIG.  9   ) disposed on the interlayer insulating layer  123  and connected to the first electrode area SDA 1  or SDA 2  of the active layer (ACT 1 , ACT 2 , and ACT 3  of  FIG.  8    and  FIG.  9   ) via a first electrode hole (EH 12 , EH 21 , EH 22 , and EH 31  of  FIG.  8    and  FIG.  9   ) defined through the interlayer insulating layer  123  to overlap or expose a portion of the first electrode area SDA 1  or SDA 2  of the active layer (ACT 1 , ACT 2 , and ACT 3  of  FIG.  8    and  FIG.  9   ). 
     In an embodiment, at least one selected from the first thin-film transistor T 1 , the second thin-film transistor T 2  and the third thin-film transistor T 3  disposed in each of the pixel areas PX of the circuit array  12 A of the thin-film transistor array substrate may further include a second electrode (DE 1 , SE 2 , DE 2 , and SE 3  in  FIG.  8    and  FIG.  9   ) disposed on the interlayer insulating layer  123  and connected to the second electrode area SDA 2  or SDA 1  of each of the active layers ACT 1 , ACT 2 , and ACT 3  via a second electrode hole EH 12 , EH 21 , EH 22 , and EH 31  defined through the interlayer insulating layer  123  to overlap or expose a portion of the second electrode area SDA 2  or SDA 1  of each of the active layers ACT 1 , ACT 2 , and ACT 3 . 
     In such an embodiment, one of the first and second electrode areas SDA 1  and SDA 2  may act as a source area SDA 1 , and the other thereof may act as a drain area SDA 2 . 
     The first electrode may act as one of the source electrode and the drain electrode, and the second electrode may act as the other of the source electrode and the drain electrode. 
     That is, at least one selected from the first thin-film transistor T 1 , the second thin-film transistor T 2 , and the third thin-film transistor T 3  disposed in each of the pixel areas PX of the circuit array  12 A of the thin-film transistor array substrate may include at least one selected from the source electrode and the drain electrode. 
     The first electrode hole EH 12 , EH 21 , EH 22 , and EH 31  may refer to the source electrode hole EH 21  and EH 31  between the source area SDA 1  of the active layer ACT 2  and ACT 3  and the source electrode SE 2  and SE 3 , or may refer to the drain electrode hole EH 12  and EH 22  between the drain area SDA 2  of the active layer ACT 1  and ACT 2  and the drain electrode DE 1  and DE 2 . 
     In an embodiment, referring to  FIG.  11   , a contact hole (CH 1 , CH 2 , and CH 3  of  FIG.  8    and  FIG.  9   ) may be defined through the interlayer insulating layer  123  and the buffer layer  121  to overlap or expose a portion of the oxygen supply layer OSL in at least one selected from the first thin-film transistor T 1 , the second thin-film transistor T 2 , and the third thin-film transistor T 3  disposed in each of the pixel areas PX of the circuit array  12 A of the thin-film transistor array substrate. The light-shielding layers LSL 1 , LSL 2 , and LSL 3  may be electrically connected to the gate electrodes GE 1 , GE 2 , and GE 3  or the first electrodes DE 1 , SE 2 , DE 2 , and SE 3  via the contact holes CH 1 , CH 2 , and CH 3 . 
     In an embodiment, as illustrated in  FIG.  10   , the second thin-film transistor T 2  of the second pixel area PX 2  may include the light-shielding layer LSL 2  disposed on the substrate  11 , the oxygen supply layer OSL including or formed of a metal oxide and disposed on the light-shielding layer LSL 2 , the active layer ACT 2  disposed on the buffer layer  121  covering the oxygen supply layer OSL 2  and including the channel area CA, the source area SDA 1  and the drain area SDA 2 , the gate insulating layer  122  disposed on the active layer ACT 2  and in the channel area CA, the gate electrode GE 2  disposed on the gate insulating layer  122 , and the source electrode SE 2  disposed on and the interlayer insulating layer  123  covering the gate electrode GE 2  and the active layer ACT 2  and connected to the source area SDA 1  of the active layer ACT 2  via the source electrode hole EH 21  defined through the interlayer insulating layer  123 . 
     The source electrode SE 2  of the second thin-film transistor T 2  of the second pixel area PX 2  may be composed of or defined by a portion of the second data line GDL. 
     In an embodiment, the drain electrode hole EH 22  defined through the interlayer insulating layer  123  in the second thin-film transistor T 2 , and the drain electrode DE is disposed on the interlayer insulating layer  123  and connected to the drain area SDA 2  of the active layer ACT 2  via the drain electrode hole EH 22 . 
     The drain electrode DE 2  of the second thin-film transistor T 2  may be connected to the gate electrode GE 1  of the first thin-film transistor T 1  via the gate electrode hole EH 13  of the first thin-film transistor T 1  defined through the interlayer insulating layer  123 . 
     The substrate  11  may include or be formed of an insulating material. In an embodiment, for example, the substrate  11  may include or be formed of an insulating material such as glass, quartz, or polymer resin. In an embodiment, the polymer resin may include polyethersulphone (“PES”), polyacrylate (“PA”), polyarylate (“PAR”), polyetherimide (“PEI”), polyethylene napthalate (“PEN”), polyethylene terepthalate (“PET”), polyphenylene sulfide (“PPS”), polyallylate, polyimide (“PI”), polycarbonate (“PC”), cellulose triacetate (“CAT”), cellulose acetate propionate (“CAP”), or combinations thereof, for example. 
     In an embodiment, the substrate  11  may be rigid to firmly support the circuit array  12  and the light-emitting array  13  disposed on the thin-film transistor array substrate  10 . 
     Alternatively, for easy deformation of the display device  1 , the substrate  11  may include or be formed of a flexible and soft insulating material that is easily bent, folded, or rolled. 
     Alternatively, the substrate  11  may include or be formed of a metal material. 
     The active layer ACT 2  may include or be formed of an oxide semiconductor. 
     In an embodiment, the oxide semiconductor may include at least one metal selected from indium (In), gallium (Ga), zinc (Zn), tin (Sn), titanium (Ti), zirconium (Zr), and hafnium (Hf), and oxygen (O). 
     The active layer ACT 2  includes or is formed of the oxide semiconductor. Thus, the thin-film transistor array substrate  10  may include the light-shielding layer LSL 2  and the oxygen supply layer OSL to reduce a difference between threshold voltages of the thin-film transistors. 
     The light-shielding layer LSL 2  may prevent external light from the substrate  11  from entering the active layer ACT 2 . In an embodiment, where the active layer ACT 2  includes or is formed of the oxide semiconductor in which semiconductor characteristic variation is caused by light, threshold voltage variation of the thin-film transistor may be reduced by the light-shielding layer LSL 2 . 
     The light-shielding layer LSL 2  may be include or formed of a conductive light-shielding material. 
     The light-shielding layer LSL 2  may overlap the channel area CA of the at least active layer ACT 2 . 
     The oxygen supply layer OSL may be subjected to a heat treatment process to supply the oxygen to the active layer ACT 2  during a manufacturing process, and may include or be formed of a metal oxide. 
     In a process of providing the gate insulating layer  122  on the channel area CA of the active layer ACT 2 , oxygen defects may be generated in the active layer ACT 2 , such that the semiconductor characteristic of the active layer ACT 2  may be deteriorated. Accordingly, excessive oxygen may be injected into the buffer layer  121  through the oxygen supply layer OSL to prevent deterioration of the semiconductor characteristic of the active layer ACT 2  during the process of providing the gate insulating layer  122  on the channel area CA of the active layer ACT 2 . When the heat treatment is performed thereon, oxygen of the buffer layer  121  may be supplied to the active layer ACT 2 . 
     Accordingly, in such an embodiment, the threshold voltage characteristic of the thin-film transistor may be improved, so that reliability of the thin-film transistor may be improved. In such an embodiment, uniformity of the threshold voltage characteristics of the plurality of thin-film transistors may be improved, and uniformity of the luminance characteristics of the plurality of pixel areas PX may be improved. 
     The oxygen supply layer OSL may include or be formed of a metal oxide including at least one selected from indium (In), gallium (Ga), zinc (Zn), tin (Sn), titanium (Ti), zirconium (Zr), and hafnium (Hf). In an embodiment, for example, the oxygen supply layer OSL may include or be formed of a same material as that of the active layer ACT 2 . In an embodiment, for example, the oxygen supply layer OSL and the active layer ACT 2  may be formed of In—Ga—Zn—O (“IGZO”). 
     The oxygen supply layer OSL may be formed using a same mask process in which the light-shielding layer LSL 2  is formed, so that the oxygen supply layer OSL may have a planar shape similar to that of the light-shielding layer LSL 2  and may be disposed on the light-shielding layer LSL 2 . 
     The buffer layer  121  is disposed over an entire surface of the substrate  11  and covers the oxygen supply layer OSL and the light-shielding layer LSL 2 . The buffer layer  121  may be composed of or defined by a single layer including or formed of at least one of silicon nitride, silicon oxide, and silicon oxynitride or multi-layers including or formed of at least one selected from silicon nitride, silicon oxide, and silicon oxynitride. 
     The active layer ACT 2  includes the channel area CA where the channel is generated, and the source area SDA 1  and the drain area SDA 2  in contact with both opposing sides of the channel area CA, respectively. The channel of the channel area CA may correspond to a difference between a voltage of one of the source area SDA 1  and the drain area SDA 2  and a voltage of the channel area CA. 
     The gate insulating layer  122  is disposed at least in the channel area CA and on the active layer ACT 2 . 
     The gate insulating layer  122  may be formed using a same mask process in which the gate electrode GE 2  to be described later is formed. Thus, the gate insulating layer  122  may be disposed under the gate electrode GE 2  while having a planar shape similar to that of the gate electrode GE 2 . 
     The gate insulating layer  122  may include a silicon compound, a metal oxide, etc. In an embodiment, for example, the gate insulating layer  122  may include at least one selected from silicon oxide, silicon nitride, silicon oxynitride, aluminum oxide, tantalum oxide, hafnium oxide, zirconium oxide, titanium oxide, and the like. 
     The gate electrode GE 2  is disposed on the gate insulating layer  122 . 
     The gate electrode GE 2  may be composed of or defined by a single layer or multi-layers, each layer including at least one selected from silver (Ag), magnesium (Mg), aluminum (Al), platinum (Pt), lead (Pb), palladium (Pd), gold (Au), nickel (Ni), neodymium (Nd), iridium (Ir), chromium (Cr), lithium (Li), calcium (Ca), and mixtures thereof. 
     Alternatively, the gate electrode GE 2  may further include a layer including or formed of a material with a high work function such as indium-tin-oxide (“ITO”), indium-zinc-oxide (“IZO”), zinc oxide (ZnO), indium oxide (In 2 O 3 ), etc. 
     The interlayer insulating layer  123  is disposed on an entire surface of the buffer layer  121  and covers the active layer ACT 2  and the gate electrode GE 2 . 
     The interlayer insulating layer  123  may include or be formed of an inorganic insulating material such as silicon oxide, silicon nitride, silicon oxynitride, hafnium oxide, aluminum oxide, titanium oxide, tantalum oxide, or zinc oxide. 
     The second thin-film transistor T 2  of the second pixel area PX 2  may include the source electrode SE 2  and the drain electrode DE 2  disposed on the interlayer insulating layer  123 . 
     The source electrode SE 2  may be connected to the source area SDA 1  of the active layer ACT 2  via the source electrode hole EH 21  defined through the interlayer insulating layer  123 . 
     The source electrode SE 2  of the second thin-film transistor T 2  of the second pixel area PX 2  may be composed of or defined by a portion of the second data line GDL. 
     The drain electrode DE 2  may be connected to the drain area SDA 2  of the active layer ACT 2  via the drain electrode hole EH 22  defined through the interlayer insulating layer  123 . 
     The drain electrode DE 2  of the second thin-film transistor T 2  may be connected to the gate electrode GE 1  of the first thin-film transistor T 1  via the gate electrode hole EH 13  of the first thin-film transistor T 1  defined through the interlayer insulating layer  123 . 
     Each of the source electrode SE 2  and the drain electrode DE 2  may include or be formed of at least one selected from silver (Ag), magnesium (Mg), aluminum (Al), platinum (Pt), lead (Pb), palladium (Pd), gold (Au), nickel (Ni), neodymium (Nd), iridium (Ir), chromium (Cr), lithium (Li), calcium (Ca), and mixtures thereof. 
     In an embodiment, the circuit array  12 A may further include a transistor protective layer  124  disposed on the interlayer insulating layer  123  and covering the source electrode SE 2  and the drain electrode DE 2 . 
     Referring to  FIG.  11   , in the second thin-film transistor T 2 , the gate electrode hole EH 23  may be defined through the interlayer insulating layer  123  to overlap or expose a portion of the gate electrode GE 2 , the contact hole CH 2  may be defined through the interlayer insulating layer  123  and the buffer layer  121  to overlap or expose a portion of the oxygen supply layer OSL, and the connective pattern CNP is disposed to connect the gate electrode hole EH 23  and the contact hole CH 2  to each other. 
     In such an embodiment, the light-shielding layer LSL 2  of the second thin-film transistor T 2  may be connected to the gate electrode GE 2  via the gate electrode hole EH 23 , the connective pattern CNP, the contact hole CH 2 , and the oxygen supply layer OSL. Accordingly, the light-shielding layer LSL 2  of the second thin-film transistor T 2  may function as an auxiliary gate electrode having a same voltage level as that of the gate electrode GE 2 . 
     In an embodiment, like the light-shielding layer LSL 2  of the second thin-film transistor T 2 , the light-shielding layer LSL 3  of the third thin-film transistor T 3  may function as an auxiliary gate electrode having a same voltage level as that of the gate electrode GE 3  of the third thin-film transistor T 3 . 
     In an embodiment, referring to  FIG.  8   , in the third thin-film transistor T 3 , the contact hole CH 3  is defined in an overlapping area between the light-shielding layer LSL 3  and the auxiliary global control line GCL′. The light-shielding layer LSL 3  may be connected to the auxiliary global control line GCL′ via the contact hole CH 3 . The gate electrode GE 3  of the third thin-film transistor T 3  is composed of or defined by a portion of a pattern branching from the global control line GCL, and the auxiliary global control line GCL′ is connected to the global control line GCL via the line hole LH. Accordingly, both the gate electrode GE 3  and the light-shielding layer LSL 3  of the third thin-film transistor T 3  may be connected to the global control line GCL and receive the global control signal therefrom, so that the light-shielding layer LSL 3  of the third thin-film transistor T 3  may function as an auxiliary gate electrode having a same voltage level as that of the gate electrode GE 3  of the third thin-film transistor T 3 . 
     Referring to  FIG.  12   , the first thin-film transistor T 1  is substantially the same as the second thin-film transistor T 2  shown in  FIG.  10    and  FIG.  11    except that the source area of the active layer ACT 1  thereof is in contact with the active layer ACT 3  of the third thin-film transistor T 3  to implement the third node ND 3 , and the drain electrode DE 1  thereof is connected to the light-shielding layer LSL 1  via the contact hole CH 1  defined through the interlayer insulating and the buffer layer  121 , and the oxygen supply layer OSL. Thus, any repetitive detailed descriptions thereof will be omitted. 
     Referring to  FIG.  12   , the third thin-film transistor T 3  is substantially the same as the second thin-film transistor T 2  shown in  FIG.  10    and  FIG.  11    except that the drain area of the active layer ACT 3  thereof is in contact with the active layer ACT 1  of the first thin-film transistor T 1  to implement the third node ND 3 , and the source electrode SE 3  is composed of a portion of the first drive power line VDL. Thus, any repetitive detailed descriptions thereof will be omitted. 
     In an embodiment, as described above with reference to  FIGS.  8 ,  10 ,  11  and  12   , each of the first, second and third thin-film transistors T 1 , T 2 , and T 3  includes the oxygen supply layer OSL disposed on each of the light-shielding layers LSL 1 , LSL 2 , and LSL 3 . Thus, the heat treatment of the oxygen supply layer may allow the semiconductor characteristics of the active layers ACT 1 , ACT 2 , and ACT 3  formed of the oxide semiconductor to be improved. As a result, the threshold voltage characteristics of the thin-film transistors T 1 , T 2 , and T 3  may be uniform, so that the luminance control of the plurality of pixel areas PX may be easily controlled, and thus the display quality of the display device  1  may be improved. 
       FIG.  13    is a cross-sectional view taken along line I-I′ in  FIG.  8    according to an alternative embodiment.  FIG.  14    is a cross-sectional view taken along line II-II′ in  FIG.  8    according to an embodiment.  FIG.  15    is a cross-sectional view taken along line III-III′ in  FIG.  8    according to an alternative embodiment. 
     In an embodiment of  FIG.  13   ,  FIG.  14    and  FIG.  15   , each of the first, second and third thin-film transistors T 1 , T 2 , and T 3  disposed in a circuit array  12 B of the thin-film transistor array substrate  10  is substantially the same as that in the embodiment described above with reference to  FIG.  10   ,  FIG.  11    and  FIG.  12    except that each of the first, second and third thin-film transistors T 1 , T 2 , and T 3  further includes an auxiliary oxygen supply layer SOSL disposed between each of the gate electrodes GE 1 , GE 2 , and GE 3  and the gate insulating layer  122 , where the auxiliary oxygen supply layer SOSL includes or is formed of a metal oxide. Thus, any repetitive detailed descriptions of the same or like elements in the embodiment of  FIG.  13   ,  FIG.  14    and  FIG.  15    as those described above with reference to  FIG.  10   ,  FIG.  11    and  FIG.  12    will hereinafter be omitted below. 
     According to an embodiment, as shown in  FIG.  13   ,  FIG.  14    and  FIG.  15   , the auxiliary oxygen supply layer SOSL and the oxygen supply layer OSL are respectively disposed above and below each of the active layers ACT 1 , ACT 2 , and ACT 3 . Thus, during the heat treatment process, the oxygen may be supplied to a top surface and a bottom surface of each of the active layers ACT 1 , ACT 2 , and ACT 3 . 
     Accordingly, sufficient oxygen supply to the active layers ACT 1 , ACT 2 , and ACT 3  may be carried out. Thus, the semiconductor characteristics in upper and lower portions of the channel area CA may be maintained to be uniform. Therefore, the threshold voltage characteristics of the thin-film transistors T 1 , T 2 , and T 3  may be further uniform. 
       FIG.  16    is a cross-sectional view taken along line II-II′ in  FIG.  8    according to another alternative embodiment.  FIG.  17    is a cross-sectional view taken along line in  FIG.  8    according to another alternative embodiment. 
     In an embodiment of  FIG.  16    and  FIG.  17   , each of the first, second and third thin-film transistors T 1 , T 2 , and T 3  disposed in a circuit array  12 C of the thin-film transistor array substrate  10  is substantially the same as that in the embodiment described above with reference to  FIG.  10   , and  FIG.  11    and  FIG.  12    except that the oxygen supply layer OSL′ and OSL″ has portions of different thicknesses from each other. Thus, any repetitive detailed descriptions of the same or like elements in the embodiment of  FIG.  16    and  FIG.  17    as those described above with reference to  FIG.  10   ,  FIG.  11    and  FIG.  12    will hereinafter be omitted. 
     According to an embodiment, as shown in  FIG.  16    and  FIG.  17   , a portion OSL′ of the oxygen supply layer disposed on each of the light-shielding layers LSL 1 , LSL 2 , and LSL 3  and corresponding to each of the contact holes CH 1 , CH 2 , and CH 3  has a first thickness TH 1 , and a remaining portion OSL″ thereof has a second thickness TH 2  smaller than the first thickness TH 1 . 
     The buffer layer  121  is disposed on the substrate  11  such that a top surface thereof is planarized. The buffer layer covers the oxygen supply layer OSL′ and OSL″. 
     Accordingly, in such an embodiment where a portion of the buffer layer  121  in contact with the substrate  11  has a third thickness TH 3 , the third thickness TH 3  of the buffer layer  121  is greater than a sum of the first thickness TH 1  of the oxygen supply layer OSL′ and a thickness of the light-shielding layer LSL 2 . 
     In such an embodiment, another portion of the buffer layer  121  covering the oxygen supply layer OSL′ of the first thickness TH 1  may have a fourth thickness TH 4  exceeding 0 and smaller than the third thickness TH 3 . In an embodiment, for example, the sum of the fourth thickness TH 4  of the buffer layer  121  and a thickness of the active layer ACT 2  may be about 300 angstrom (Å) or smaller. 
     In such an embodiment, the fourth thickness TH 4  of the portion of the buffer layer  121  corresponding to each of the contact holes CH 1 , CH 2 , and CH 3  is small. Thus, even when each of the contact holes CH 1 , CH 2  and CH 3  defined through the interlayer insulating layer  123  and the buffer layer  121  and each of the source electrode holes EH 21  and EH 31 , the drain electrode holes EH 12  and EH 22  and the gate electrode holes EH 13  and EH 23  defined through the interlayer insulating layer  123  are formed in a same etching process, a probability that each of the active layers ACT 1 , ACT 2 , and ACT 3  is damaged due to excessive etching may be lowered. 
     As described above, according to an embodiment, even when each of the contact holes CH 1 , CH 2 , and CH 3  defined through the interlayer insulating layer  123  and the buffer layer  121  and each of the source electrode holes EH 21  and EH 31 , the drain electrode holes EH 12  and EH 22  and the gate electrode holes EH 13  and EH 23  defined through the interlayer insulating layer  123  are formed in a same etching process, the damage to each of the active layers ACT 1 , ACT 2 , and ACT 3  due to the excessive etching may be prevented such that a method for manufacturing the thin film transistor may be simplified. 
     Next, a method for manufacturing a thin-film transistor according to embodiments will be described. 
       FIG.  18    and  FIG.  19    are flowcharts showing a method for manufacturing a thin-film transistor according to an embodiment.  FIG.  20   ,  FIG.  21   ,  FIG.  22   ,  FIG.  23   ,  FIG.  24   ,  FIG.  25   ,  FIG.  26   ,  FIG.  27   ,  FIG.  28   ,  FIG.  29   ,  FIG.  30   ,  FIG.  31   ,  FIG.  32   ,  FIG.  33   ,  FIG.  34    and  FIG.  35    are cross-sectional views showing processes of  FIG.  18    and  FIG.  19   . More particularly,  FIG.  18    and  FIG.  19    are flowcharts showing an embodiment of a method for manufacturing a thin-film transistor of  FIG.  8   ,  FIG.  10   ,  FIG.  11    and  FIG.  12   . 
     Referring to  FIG.  18    and  FIG.  19   , an embodiment of the method for manufacturing the thin-film transistor may include a process S 11  of sequentially stacking (or providing) a light-shielding conductive material film and a metal oxide material film on the substrate  11 , a process S 12  of disposing (or providing or depositing) a photoresist mask layer on the metal oxide material film  202 , a process S 13  of disposing (or forming) the oxygen supply layer OSL by patterning the metal oxide material film  202  using the photoresist mask layer disposed thereon, a process S 14  of disposing (or forming) each of the light-shielding layers LSL 1 , LSL 2 , and LSL 3  by patterning the light-shielding conductive material film  201  while maintaining the photoresist mask layer  301 , a process S 15  of removing the photoresist mask layer, a process S 20  of disposing (or providing) the buffer layer  121  covering the oxygen supply layer OSL on the substrate  11 , a process S 30  of disposing (or forming) each of the active layers ACT 1 , ACT 2 , and ACT 3  including the channel area CA and the first and second electrode areas SDA 1  and SDA 2  in contact with both opposing sides of the channel area CA, respectively, by patterning a semiconductor material film on the buffer layer  121 , a process S 40  of disposing (or forming) the gate insulating layer  122  and each of the gate electrodes GE, GE 2 , and GE 3  which overlaps the channel area CA of each of the active layers ACT 1 , ACT 2 , and ACT 3 , and are sequentially stacked, by patterning an insulating material film covering each of the active layers ACT 1 , ACT 2 , and ACT 3  and a first conductive material film on the insulating material film, a process S 50  of disposing (or providing) the interlayer insulating layer  123  covering each of the active layers ACT 1 , ACT 2 , and ACT 3  and each of the gate electrodes GE 1 , GE 2 , and GE 3  on the buffer layer  121 , a process S 60  of forming each of the first electrode holes EH 21 , EH 31 , EH 12 , and EH 22  corresponding to a portion of each of the active layers ACT 1 , ACT 2 , and ACT 3  and each of the contact holes CH 1 , CH 2  and CH 3  corresponding to a portion of the oxygen supply layer OSL by patterning the interlayer insulating layer  123  and the buffer layer  121 , and a process S 70  of disposing (or forming) each of the first electrodes DE 1 , SE 2 , DE 2 , and SE 3  connected to each of the active layers ACT 1 , ACT 2 , and ACT 3  via each of the first electrode holes EH 21 , EH 31 , EH 12 , and EH 22  by patterning a second conductive material film on the interlayer insulating layer  123 . 
     Referring to  FIG.  20   , the substrate  11  including the display area is prepared. Then, the process S 11  of sequentially stacking the light-shielding conductive material film  201  and the metal oxide material film  202  on one surface of the substrate  11  is performed. 
     In an embodiment, for example, the light-shielding conductive material film  201  may include or be formed of a metal material. 
     The metal oxide material film  202  may include or be formed of a metal oxide including at least one selected from indium (In), gallium (Ga), zinc (Zn), tin (Sn), titanium (Ti), zirconium (Zr), and hafnium (Hf). In an embodiment, for example, the metal oxide material film  202  may include or be formed of IGZO. 
     Referring to  FIG.  21   , the process S 12  of disposing the photoresist mask layer  301  on the metal oxide material film  202  is performed. 
     The photoresist mask layer  301  may include or be formed of a material having a relatively low etch rate. The photoresist mask layer  301  may include or be formed of a photoreactive material which is cured in an amount varying depending on an exposure amount to light. 
     Referring to  FIG.  22   , the process S 13  is performed to pattern the metal oxide material film  202  in a state where the photoresist mask layer  301  is disposed thereon to prepare the oxygen supply layer OSL. 
     In an embodiment, the patterning of the metal oxide material film  202  may be performed using wet etching. 
     In an embodiment, the patterning of the metal oxide material film  202  may allow a remaining portion of the metal oxide material film  202  except for a portion thereof corresponding to the photoresist mask layer  301  to be removed using wet etching. Thus, the oxygen supply layer OSL composed of or defined by the portion thereof corresponding to the photoresist mask layer  301  may be formed. 
     Referring to  FIG.  23   , the process S 14  of preparing each of the light-shielding layers LSL 1 , LSL 2 , and LSL 3  by patterning the light-shielding conductive material film  201  while maintaining the photoresist mask layer  301  is performed. 
     In an embodiment, the patterning of the light-shielding conductive material film  201  may be performed using dry etching. 
     In an embodiment, the patterning of the light-shielding conductive material film  201  may allow the remainder of the light-shielding conductive material film  201  except for a portion thereof corresponding to the photoresist mask layer  301  to be removed using the dry etching, so that each of the light-shielding layers LSL 1 , LSL 2 , and LSL 3  composed of the portion thereof corresponding to the photoresist mask layer  301  may be provided. 
     Then, referring to  FIG.  24   , the process S 15  of removing the photoresist mask layer  301  is performed. 
     Thus, as shown in  FIG.  24    and  FIG.  25   , each of the light-shielding layers LSL 1 , LSL 2 , and LSL 3  and the oxygen supply layer OSL on each of the light-shielding layers LSL 1 , LSL 2 , and LSL 3  of each of the first, second and third thin-film transistors T 1 , T 2 , and T 3  are prepared. 
     Referring to  FIG.  26   , the process S 20  of applying an insulating material film on the substrate  11  to form the buffer layer  121  covering the oxygen supply layer OSL is performed. 
     The buffer layer  121  may be composed of or defined by a single layer or multi-layers, each layer therein including or formed of at least one selected from silicon nitride, silicon oxide, and silicon oxynitride. 
     Referring to  FIG.  27    and  FIG.  28   , the process S 30  of patterning the semiconductor material film (not shown) on the buffer layer  121  to form each of the active layers ACT 1 , ACT 2 , and ACT 3  of each of the first, second and third thin-film transistors T 1 , T 2 , and T 3  is performed. 
     Each of the active layers ACT 1 , ACT 2 , and ACT 3  may include or be formed of an oxide semiconductor including at least one selected from indium (In), gallium (Ga), zinc (Zn), tin (Sn), titanium (Ti), zirconium (Zr), and hafnium (Hf). In an embodiment, for example, each of the active layers ACT 1 , ACT 2 , and ACT 3  may include or be formed of IGZO. Each of the active layers ACT 1 , ACT 2 , and ACT 3  may be formed of a same material as that of the oxygen supply layer OSL. 
     Referring to  FIG.  29    and  FIG.  30   , the process S 40  of patterning the insulating material film  203  covering each of the active layers ACT 1 , ACT 2 , and ACT 3  and the first conductive material film  204  on the insulating material film  203  to form the gate insulating layer  122  and each of the gate electrodes GE 1 , GE 2 , and GE 3  is performed. 
     The insulating material film  203  and the first conductive material film  204  may be patterned based on a photomask  302  at the same time. Accordingly, the gate insulating layer  122  and each of the gate electrodes GE 1 , GE 2 , and GE 3  may have a similar planar shape as each other. 
     The gate insulating layer  122  may be composed of or defined by a single layer or multi-layers, each layer therein including or formed of at least one selected from silicon nitride, silicon oxide, and silicon oxynitride. 
     Each of the gate electrodes GE 1 , GE 2 , and GE 3  are insulated from each of the active layers ACT 1 , ACT 2 , and ACT 3  via the gate insulating layer  122 , and overlaps with the channel area CA of each of the active layers ACT 1 , ACT 2 , and ACT 3 . 
     Referring to  FIG.  31   , the process S 50  of applying the insulating material film on the buffer layer  121  to form the interlayer insulating layer  123  covering each of the active layers ACT 1 , ACT 2 , and ACT 3  and each of the gate electrodes GE 1 , GE 2 , and GE 3  is performed. 
     The interlayer insulating layer  123  may be composed of or defined by a single layer or multi-layers, each layer therein including or formed of an inorganic insulating material or an organic insulating material. 
     Referring to  FIG.  32    and  FIG.  33   , the process S 60  of patterning the interlayer insulating layer  123  and the buffer layer  121  to form each of the first electrode holes EH 21 , EH 31 , EH 12 , and EH 22  and each of the contact holes CH 1 , CH 2 , and CH 3  is performed. 
     In an embodiment, the first electrode holes EH 21 , EH 31 , EH 12 , and EH 22  may include each of the source electrode holes EH 21 , and EH 31 , or each of the drain electrode holes EH 12 , and EH 22  that formed through the interlayer insulating layer  123  to overlap or expose a portion of each of the active layers ACT 1 , ACT 2 , and ACT 3 . 
     In an embodiment, each of the contact holes CH 1 , CH 2 , and CH 3  is formed through the interlayer insulating layer  123  and the buffer layer  121 , to overlap or expose a portion of the oxygen supply layer OSL. 
     In an embodiment, the gate electrode holes EH 13  and EH 23  defined through the interlayer insulating layer  123  to overlap or expose portions of the gate electrodes GE 1  and GE 2 , respectively may be formed at the same time in the process S 60  of forming the first electrode holes EH 21 , EH 31 , EH 12 , and EH 22  and the contact holes CH 1 , CH 2 , and CH 3 . 
     In an embodiment, the formation of the first electrode holes EH 21 , EH 31 , EH 12 , and EH 22  and the formation of the contact holes CH 1 , CH 2 , and CH 3  may be performed in different mask processes. 
     Alternatively, the first electrode holes EH 21 , EH 31 , EH 12 , and EH 22  and the contact holes CH 1 , CH 2 , and CH 3  may be simultaneously formed in a same mask process to reduce the number of mask processes. In such an embodiment, depending on a thickness of the buffer layer  121 , a portion of each of the active layers ACT 1 , ACT 2 , and ACT 3  exposed through each of the first electrode holes EH 21 , EH 31 , EH 12 , and EH 22  may be damaged. 
     Referring to  FIG.  34    and  FIG.  35   , the process S 70  of patterning the second conductive material film (not shown) on the interlayer insulating layer  123  to form each of the first electrodes DE 1 , SE 2 , DE 2 , and SE 3  is performed. 
     In an embodiment, the first electrodes DE 1 , SE 2 , DE 2 , and SE 3  may include each of the source electrodes SE 2  and SE 3  or each of the drain electrodes DE 1  and DE 2  connected to each of the active layers ACT 1 , ACT 2 , and ACT 3  via each of the first electrode holes EH 21 , EH 31 , EH 12 , and EH 22 . 
     In an embodiment, as the first electrode, the drain electrode DE 1  of the first thin-film transistor T 1  may be connected to the drain area SDA 2  of the active layer ACT 1  via the drain electrode hole EH 12 , and may be connected to the light-shielding layer LSL 1  via the contact hole CH 1  and the oxygen supply layer OSL. 
     The connective pattern CNP of the second thin-film transistor T 2  may be formed at the same time in the process S 70  of forming the first electrodes DE 1 , SE 2 , DE 2 , and SE 3 . In an embodiment, the connective pattern CNP may be connected to the gate electrode GE 2  of the second thin-film transistor T 2  via the gate electrode hole EH 23  of the second thin-film transistor T 2  formed through the interlayer insulating layer  123  and may be connected to the light-shielding layer LSL 2  via the contact hole CH 2  formed through the interlayer insulating layer  123  and the buffer layer  121  and the oxygen supply layer OSL. In such an embodiment, the light-shielding layer LSL 2  of the second thin-film transistor T 2  may be connected to the gate electrode GE 2  via the connective pattern CNP and thus may function as the auxiliary gate electrode. 
     Although not shown separately, an embodiment of the method for manufacturing the thin-film transistor of  FIG.  13    is the same as the embodiment of the method for manufacturing the thin-film transistor of  FIG.  10    described above, except that in the process S 40  of forming the gate insulating layer  122  and the gate electrodes GE 1 , GE 2 , GE 3  further includes patterning an additional metal oxide material film (not shown) disposed between the insulating material film ( 203  in  FIG.  29   ) and the first conductive material film ( 204  in  FIG.  29   ) together with the insulating material film ( 203  in  FIG.  29   ) and the first conductive material film ( 204  in  FIG.  29   ) to form the auxiliary oxygen supply layer (SOSL of  FIG.  13   ,  FIG.  14   , and  FIG.  15   ) disposed between the gate insulating layer  122  and each of the gate electrodes GE 1 , GE 2 , and GE 3 . Thus, any repetitive detailed descriptions thereof will be omitted. 
       FIG.  36    and  FIG.  37    are flowcharts showing a method for manufacturing the thin-film transistor according to an alternative embodiment.  FIG.  38   ,  FIG.  39   ,  FIG.  40   , FIG.  41 ,  FIG.  42   ,  FIG.  43    and  FIG.  44    are cross-sectional views showing processes of  FIG.  36    and  FIG.  37   . More particularly,  FIG.  36    and  FIG.  37    are flowcharts showing an embodiment of a method for manufacturing a thin-film transistor of  FIG.  8   ,  FIG.  16    and  FIG.  17   . 
     Referring to  FIG.  36    and  FIG.  37   , an alternative embodiment of the method for manufacturing the thin-film transistor is the same as the embodiment of the method for manufacturing the thin-film transistor of  FIG.  18    and  FIG.  19    except that a photoresist mask layer including first and second mask portions of different thicknesses is used in the process S 12  of disposing the photoresist mask layer of  FIG.  18   , and the method further includes a process S 16  of removing the second mask portion of the photoresist mask layer and a process S 17  of additionally patterning the oxygen supply layer OSL between the process S 14  of forming the light-shielding layer of  FIG.  18    and the process S 15  of removing the photoresist mask layer of  FIG.  19   , and the method further includes a process S 21  of planarizing the buffer layer after the process S 20  of forming the buffer layer of  FIG.  19   . Thus, any repetitive detailed descriptions of the same or like elements thereof as those described above will hereinafter be omitted. 
     Referring to  FIG.  38   , in the process S 12  of forming the photoresist mask layer  303 , a photoresist mask layer  303  includes the first mask portion of a first mask thickness MTH 1 , and the second mask portion of a second mask thickness MTH 2  smaller than the first mask thickness MTH 1 . In an embodiment, for example, the photoresist mask layer  303  including the first and second mask portions may be embodied as a halftone exposure mask. 
     In such an embodiment, the first mask portion of the first mask thickness MTH 1  corresponds to the contact holes CH 1 , CH 2 , and CH 3  to be described later. 
     Referring to  FIG.  39   , after the processes S 13  and S 14  of preparing each of the light-shielding layers LSL 1 , LSL 2 , and LSL 3  and the oxygen supply layer OSL using the photoresist mask layer  303 , the process S 16  of removing the second mask portion of the mask thickness MTH 2  from the photoresist mask layer  303  is performed. In an embodiment, for example, the process S 16  of removing the second mask portion may be performed by performing an ashing process on the photoresist mask layer  303 . 
     Accordingly, the second mask portion is removed from the photoresist mask layer  303 , and a first mask portion  303 ′ having a thickness smaller than the first mask thickness MTH 1  remains. 
     Referring to  FIG.  40   , the process S 17  of additionally patterning the oxygen supply layer (OSL in  FIG.  39   ) based on the remaining first mask portion  303 ′ is performed. 
     In such an embodiment, the portion OSL′ of the oxygen supply layer corresponding to the first mask portion  303 ′ is not patterned and thus has a first thickness TH. The other portion OSL″ thereof is patterned and thus has a second thickness TH 2  smaller than the first thickness TH 1 . 
     Referring to  FIG.  41   , after the oxygen supply layer OSL′ of the first thickness TH 1  and the oxygen supply layer OSL″ of the second thickness TH 2  are prepared, the process S 15  of removing the first mask portion  303 ′ is performed. 
     Referring to  FIG.  42   , the process S 20  of applying the insulating material film on the substrate  11  to form the buffer layer  121  covering the oxygen supply layer OSL′ of the first thickness TH 1  and the oxygen supply layer OSL″ of the second thickness TH 2  is performed. 
     In an embodiment, the buffer layer  121  has a shape including a convex portion corresponding to the oxygen supply layer OSL′ of the first thickness TH 1 . 
     Referring to  FIG.  43   , a process S 21  of planarizing the buffer layer  121  is performed. 
     In an embodiment, a portion of the buffer layer  121  in contact with the substrate  11  has a third thickness TH 3 , while the other portion thereof covering the oxygen supply layer OSL′ of the first thickness TH 1  has a fourth thickness TH 4  smaller than the third thickness TH 3 . 
     The third thickness TH 3  exceeds the sum of the thickness of each of the light-shielding layers LSL 1 , LSL 2 , and LSL 3  and the first thickness TH 1  of the oxygen supply layer OSL′. Accordingly, the oxygen supply layer OSL′ of the first thickness TH 1  may also be covered with the buffer layer  121 . 
     Referring to  FIG.  44   , in the process S 60  of forming the first electrode holes EH 21 , EH 31 , EH 12 , and EH 22  and the contact holes CH 1 , CH 2 , and CH 3 , the first electrode holes EH 21 , EH 31 , EH 12 , and EH 22  and the contact holes CH 1 , CH 2 , and CH 3  may be performed simultaneously in a same mask process. 
     In an embodiment, a portion of each of the active layers ACT 1 , ACT 2 , and ACT 3  exposed to each of the first electrode holes EH 21 , EH 31 , EH 12 , and EH 22  is exposed to etching until each of the contact holes CH 1 , CH 2 , and CH 3  is formed. That is, as the fourth thickness TH 4  of the buffer layer  121  is larger, the portion of each of the active layers ACT 1 , ACT 2 , and ACT 3  exposed to each of the first electrode holes EH 21 , EH 31 , EH 12 , and EH 22  may be damaged due to excessive etching. 
     Accordingly, the fourth thickness TH 4  of the buffer layer  121  may be set to a value in a range such that each of the active layers ACT 1 , ACT 2 , and ACT 3  is not damaged due to the etching in the process S 60  of forming each of the contact holes CH 1 , CH 2 , and CH 3 . 
     In an embodiment, for example, the sum of the fourth thickness TH 4  and the thicknesses of each of the active layers ACT 1 , ACT 2 , and ACT 3  may be about 300 Å or smaller. 
     As described above, according to an embodiment, the portion of the buffer layer  121  corresponding to each of the contact holes CH 1 , CH 2 , and CH 3  is formed to have the relatively smaller fourth thickness TH 4 , using the oxygen supply layer OSL′ and OSL″ provided to supply the oxygen to each of the active layers ACT 1 , ACT 2 , and ACT 3 . Accordingly, while each of the first electrode holes EH 21 , EH 31 , EH 12 , and EH 22 , and each of the contact holes CH 1 , CH 2 , and CH 3  are formed in a same mask process such that the number of mask processes is reduced, a time duration for which each of the active layers ACT 1 , ACT 2 , and ACT 3  is exposed to the etching process until each of the contact holes CH 1 , CH 2 , and CH 3  is formed may be reduced, thereby preventing the damage to each of the active layers ACT 1 , ACT 2 , and ACT 3 . Accordingly, the manufacturing process of the thin-film transistor may be simplified, and at the same time, deterioration of the characteristics of the thin-film transistor may be effectively prevented. 
     The invention should not be construed as being limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete and will fully convey the concept of the invention to those skilled in the art. 
     While the invention has been particularly shown and described with reference to embodiments thereof, it will be understood by those of ordinary skill in the art that various changes in form and details may be made therein without departing from the spirit or scope of the invention as defined by the following claims.