Patent Publication Number: US-2022216373-A1

Title: Display device and manufacturing method therefor

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims priority to Korean Patent Application No. 10-2019-0059328 filed on May 21, 2019, and all the benefits accruing therefrom under 35 U.S.C. 119, the contents of which in its entirety are herein incorporated by reference. 
     TECHNICAL FIELD 
     The disclosure relates to a display device and a manufacturing method thereof 
     BACKGROUND ART 
     The importance of display devices is increasing with the development of multimedia. Accordingly, various types of display devices such as organic light-emitting display (“OLED”) devices and liquid crystal display (“LCD”) devices are being used. 
     A display panel such as an OLED panel or an LCD panel is a device included in a display device to display an image. Among such display panels, a light-emitting element may be provided as a light-emitting display panel, and examples of a light-emitting diode (“LED”) include an organic LED (OLED) using an organic material as a fluorescent material and an inorganic LED using an inorganic material as a fluorescent material. 
     An inorganic LED using an inorganic semiconductor as a fluorescent material has durability even in a high-temperature environment and has higher efficiency in blue light compared to the organic LED. In a manufacturing process pointed out as a limit of an existing inorganic LED element, a transfer method using a dielectrophoresis (“DEP”) method has been developed. Accordingly, research is being continuously conducted on the inorganic light-emitting diode having higher durability and efficiency than those of the organic light-emitting diode. 
     DISCLOSURE 
     Technical Problem 
     The disclosure is directed to providing a display device in which a structure located between neighboring pixels is omitted and a degree of alignment of light-emitting elements is improved. 
     The disclosure is also directed to providing a manufacturing method of a display device, in which a light-emitting element is selectively disposed in a certain region. 
     It should be noted that aspects of the disclosure are not limited thereto and other aspects, which are not mentioned herein, will be apparent to those of ordinary skill in the art from the following description. 
     Technical Solution 
     According to an embodiment of the disclosure, a display device comprises a substrate, a first electrode and a second electrode disposed on the substrate to be spaced apart from each other, a first insulating layer disposed on the substrate to cover at least a portion of the first electrode and a portion of the second electrode, and at least one first light-emitting element disposed on the first insulating layer and between the first electrode and the second electrode, and the first insulating layer comprises a first sub-insulating layer including a first portion containing a hydrophilic material and a second portion which is a region of the first insulating layer except for the first portion and which contains a hydrophobic material, and a second sub-insulating layer disposed below the first sub-insulating layer, and at least a portion of the at least one first light-emitting element is disposed on the first portion. 
     The first portion may be located between the first electrode and the second electrode. 
     An angle of contact between the first portion and water may be 5 degrees or less, and an angle of contact between the second portion and water may be 100 degrees or more. 
     The first insulating layer may comprise silicon oxycarbide, the first portion may have a higher concentration of oxygen atoms than the second portion, and the second portion may have a higher concentration of fluorine atoms than the first portion. 
     The first portion may be disposed to partially overlap a first side of the first electrode and a second side of the second electrode facing the first side of the first electrode. 
     The second portion may overlap a second side of the first electrode which does not face the second side of the second electrode, and a first side of the second electrode which does not face the first side of the first electrode. 
     A first region in which the first portion may be located and a second region in which the second portion is located are defined, and the second region may surround the first region. 
     The at least one first light-emitting element in the first region may have a higher density than the at least one first light-emitting element in the second region. 
     An emission area, to which light from the at least one first light-emitting element is emitted, may be defined, and the emission area may comprise the first region. 
     The display device may further comprise a third electrode and a fourth electrode disposed on the substrate and spaced apart from each other, and the first insulating layer may be also disposed on the third electrode and the fourth electrode, the first portion may be also located between the third electrode and the fourth electrode, and the second portion may be located between the third electrode and the first electrode. 
     The display device may further comprise at least one second light-emitting element disposed on the first portion and between the third electrode and the fourth electrode, and the at least one second light-emitting element may emit light having a different wavelength band from a wavelength band of the first-light emitting element. 
     According to an embodiment of the disclosure, a display device comprise: a substrate, a first electrode disposed on the substrate and extending in a first direction, a second electrode extending in the first direction and spaced apart from the first electrode in a second direction different from the first direction, a first insulating layer disposed to cover at least a portion of the first electrode and at least a portion of the second electrode, and at least one light-emitting element disposed on the first insulating layer and between the first electrode and the second electrode, and the first insulating layer comprises: a first portion including a hydrophilic material and located in a region between the first electrode and the second electrode, and a second portion which includes a hydrophobic material and is a region of the first insulating layer except for the first portion. 
     The display device may further comprise a third electrode spaced apart from the first electrode in the second direction, and the first insulating layer may extend to be disposed on the third electrode, the second portion is located between the first electrode and the third electrode, and the light-emitting elements between the first electrode and the second electrode may have a higher density than a density of the light-emitting elements between the first electrode and the third electrode. 
     An angle of contact between the first portion and water may be 5 degrees or less, and an angle of contact between the second portion and water may be 100 degrees or more. 
     The first insulating layer may further comprise a sub-insulating layer located below the first portion and the second portion. 
     The first portion may be provided in plural, at least two first portions of the plurality of first portions may be spaced apart from each other in the second direction, and the second portion may be located in a region between the at least two first portions. 
     According to an embodiment of the disclosure, a manufacturing method of a display device, comprises forming a substrate, a first electrode and a second electrode disposed on the substrate to be spaced apart from each other, and a first insulating layer covering at least a portion of the first electrode and the second electrode, forming, on the first insulating layer, a first portion including a hydrophilic material and a second portion including a hydrophobic material, and disposing a light-emitting element on the first portion and between the first electrode and the second electrode. 
     The forming of the first portion and the second portion may comprise forming the second portion by emitting a first plasma to the first insulating layer, and forming the first portion by emitting a second plasma to the first portion between the first electrode and the second electrode. 
     The first insulating layer may comprise silicon oxycarbide, the first plasma may comprise a fluorine (F)-based plasma, and the second plasma may comprise an oxygen (O)-based plasma. 
     The first insulating layer may further comprise a sub-insulating layer located below the first portion and the second portion. 
     The details of other embodiments are included in the detailed description and the accompanying drawings. 
     Advantageous Effects 
     A display device according to an embodiment may include a first insulating layer including a hydrophilic area and a hydrophobic area, and a light-emitting element may be selectively disposed in the hydrophilic area. In the display device, the number of light-emitting elements remaining in a region, except for a region in which light-emitting elements are disposed, may be minimized, and light-emitting elements may be aligned at a certain position even when a structure between adjacent pixels is omitted. Accordingly, in the display device, light-emitting elements may be aligned in a pixel to be distinguished from other pixels even when a size of each pixel is reduced. 
     The effects according to the embodiments are not limited by the contents exemplified above, and more various effects are included in this disclosure. 
    
    
     
       DESCRIPTION OF DRAWING 
         FIG. 1  is a schematic plan view of a display device according to an embodiment. 
         FIG. 2  is a schematic plan view of a pixel of a display device according to an embodiment. 
         FIG. 3  is a schematic cross-sectional view taken along line X 1 -X 1 ′ of  FIG. 2 . 
         FIG. 4  is an enlarged view of a portion Q of  FIG. 3 . 
         FIG. 5  is a schematic diagram illustrating that ink is sprayed on a first insulating layer according to an embodiment. 
         FIG. 6  is a schematic cross-sectional view taken along line X 2 -X 2 ′ of  FIG. 2 . 
         FIG. 7  is a cross-sectional view schematically illustrating a partial cross section of a display device according to an embodiment. 
         FIG. 8  is a cross-sectional view taken along lines Xa-Xa′, Xb-Xb′ and Xc-Xc′ of  FIG. 2 . 
         FIG. 9  is a schematic diagram of a light-emitting element according to an embodiment. 
         FIG. 10  is a flowchart of a manufacturing method of a display device according to an embodiment. 
         FIGS. 11 to 18  are schematic diagrams illustrating a manufacturing process of a display device according to an embodiment. 
         FIGS. 19 and 20  are plan views illustrating sub-pixels of display devices according to other embodiments. 
         FIG. 21  is a plan view of a sub-pixel of a display device according to another embodiment. 
         FIG. 22  is a cross-sectional view schematically illustrating a cross section of a sub-pixel of the display device of  FIG. 21 . 
         FIG. 23  is a plan view of a sub-pixel of a display device according to another embodiment. 
         FIG. 24  is a cross-sectional view schematically illustrating a cross section of a sub-pixel of the display device of  FIG. 23 . 
         FIG. 25  is a plan view illustrating three sub-pixels of the display device of  FIG. 23 . 
         FIGS. 26 to 28  are schematic cross-sectional views illustrating some operations of a manufacturing process of the display device of  FIG. 25 . 
         FIG. 29  is a schematic diagram of a light-emitting element according to another embodiment. 
     
    
    
     MODES OF THE INVENTION 
     The invention will now be described more fully hereinafter with reference to the accompanying drawings, in which preferred embodiments of the invention are shown. This invention may, however, be embodied in 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 filly convey the scope of the invention to those skilled in the art. 
     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. The same reference numbers indicate the same components throughout the specification. 
     It will be understood that, although the terms “first,” “second,” etc. may be used herein to describe various elements, these elements should not be limited by these terms. These terms are only used to distinguish one element from another element. For instance, a first element discussed below could be termed a second element without departing from the teachings of the invention. Similarly, the second element could also be termed the first element. 
     Hereinafter, embodiments will be described with reference to the accompanying drawings. 
       FIG. 1  is a schematic plan view of a display device according to an embodiment. 
     Referring to  FIG. 1 , a display device  10  displays a video or a still image. The display device  10  may refer to all types of electronic devices that provide a display screen. Examples of the display device  10  may include a television, a notebook computer, a monitor, a billboard, an internet-of-things (“IoT”) device, a mobile phone, a smartphone, tablet personal computer (“PC”), an electronic watch, a smart watch, a watch phone, ahead-mounted display, a mobile communication terminal, an electronic notebook, an e-book reader, a portable multimedia player (“PMP”), a navigation device, a game console, a digital camera, a camcorder, or the like, which provide a display screen. 
     The display device  10  includes a display panel for providing a display screen. Examples of the display panel include a light-emitting diode (LED) display panel, an organic light-emitting display panel, a quantum dot light-emitting display panel, a plasma display panel, a field-emission display panel, or the like. A case in which an LED display panel is applied as an example of a display panel will be described below, but embodiments are not limited thereto and another type of a display panels may be applied provided that the same technical idea is applicable thereto. 
     The display device  10  may be embodied in various shapes. For example, the display device  10  may have a shape such as a rectangular shape that is long in a horizontal direction, a rectangular shape that is long in a vertical direction, a square shape, a quadrangle with round corners (vertices), another polygonal shape, or a round shape. A shape of a display area DA of the display device  10  may be substantially similar to that of the display device  10 .  FIG. 1  illustrates the display device  10  and the display area DA each having a rectangular shape that is long in the horizontal direction. 
     The display device  10  may include the display area DA and a non-display area NDA. The display area DA is an area in which a screen is displayed, and the non-display area NDA is an area in which no screen is displayed. The display area DA may be referred to as an active area, and the non-display area NDA may be referred to as an inactive area. 
     In general, the display area DA may be a central area of the display device  10 . The display area DA may include a plurality of pixels PX. The plurality of pixels PX may be arranged in a matrix. Each of the plurality of pixels PX may have a rectangular or square shape on a plane but is not limited thereto and may be a rhombus shape, each side of which is inclined with respect to a first direction DR1. Each of the plurality of pixels PX may include at least one light-emitting element  300  that emits light of a certain wavelength band to display a certain color. 
       FIG. 2  is a schematic plan view of a pixel of a display device according to an embodiment. 
     Referring to  FIG. 2 , each of a plurality of pixels PX may include a first sub-pixel PX 1 , a second sub-pixel PX 2 , and a third sub-pixel PX 3 . The first sub-pixel PX 1  may emit light of a first color, and the second sub-pixel PX 2  may emit light of a second color, and the third sub-pixel PX 3  may emit light of a third color. The first color may be red, the second color may be green, the third color may be blue, but embodiments according to the invention are not limited thereto, and sub-pixels PXn may emit light of the same color in another embodiment.  FIG. 2  illustrates that each pixel PX includes three sub-pixels PXn, but is not limited thereto and may include more than three sub-pixels PXn in another embodiment. 
     As used herein, the terms “first,” “second,” etc. are used to simply distinguish components from each other rather than to limit the components. That is, configurations defined by the term “first,” ‘second” or the like are not necessarily limited to specific configurations or positions and other numbers may be assigned thereto in some cases. Thus, the number assigned to each component herein may be described with reference to the drawings and the following description, and a first component referred to hereinafter may be named a second component within the technical idea of the disclosure. 
     Each of sub-pixels PXn of the display device  10  may include an area defined as an emission area EMA. The first sub-pixel PX 1  may include a first emission area EMA 1 , the second sub-pixel PX 2  may include a second emission area EMA 2 , and the third sub-pixel PX 3  may include a third emission area EMA 3 . The emission area EMA may be defined as an area in which a light-emitting element  300  included in the display device  10  is disposed to emit light of a certain wavelength band. The light-emitting element  300  may include an active layer  330  illustrated in  FIG. 9  as will be described below, and the active layer  330  may emit light of a certain wavelength band without directionality. That is, light emitted from the active layer  330  of the light-emitting element  300  may be emitted in directions toward sides of the light-emitting element  300 , as well as in directions toward opposite distal ends of the light-emitting element  300 . The emission area EMA of each sub-pixel PXn may include an area in which the light-emitting element  300  is disposed and an area which is located adjacent to the light-emitting element  300  and to which light is emitted from the light emitting element  300 . However, embodiments according to the invention are not limited thereto, and the emission area EMA may further include an area to which light emitted from the light-emitting element  300  is reflected or refracted by another member in another embodiment. A plurality of light-emitting elements  300  may be disposed in each sub-pixel PXn, and an emission area EMA may include an area in which the plurality of light-emitting elements  300  are disposed and areas adjacent to this area. 
     Although not shown in the drawings, each sub-pixel PXn of the display device  10  may include a non-emission area defined as a region except for the emission area EMA. The non-emission area may be defined as an area in which the light-emitting element  300  is not disposed and to which light is not emitted because light emitted from the light-emitting element  300  does not reach. 
     Each sub-pixel PXn of the display device  10  may include a plurality of electrodes  210  and  220 , the light-emitting element  300 , and at least one insulating layer, e.g., insulating layers  510 ,  520 , and  550  illustrated in  FIG. 8 . 
     The plurality of electrodes  210  and  220  may be electrically connected to the light-emitting elements  300 , and a certain voltage may be applied thereto so that the light-emitting elements  300  may emit light of a certain wavelength band. At least a portion of each of the plurality of electrode  210  and  220  may be used to form an electric field in each sub-pixel PXn so as to align the light-emitting elements  300 . 
     The plurality of electrodes  210  and  220  may include a first electrode  210  and a second electrode  220 . In an embodiment, the first electrodes  210  may be pixel electrodes separated for sub-pixels PXn, and the second electrode  220  may be a common electrode commonly connected along the sub-pixels PXn. One of the first and second electrodes  210  and  220  may be an anode electrode of the light-emitting element  300 , and the other may be a cathode electrode of the light-emitting element  300 . However, embodiments according to the invention are not limited thereto, and vice versa in another embodiment. 
     The first electrode  210  and the second electrode  220  may include electrode stem portions  210 S and  220 S extending in a first direction DR1 and at least one electrode branch portion, e.g., electrode branch portions  210 B and  220 B branching from the electrode stem portions  210 S and  220 S, respectively, and extending in a second direction DR2 crossing the first direction DR1. 
     The first electrode  210  may include the first electrode stem portion  210 S extending in the first direction DR1 and at least one first electrode branch portion  210 B branching from the first electrode stem portion  210 S and extending in the second direction DR2. 
     A first electrode stem portion  210 S of a pixel may have opposite ends between sub-pixels PXn to be spaced apart from each other, and may be located in substantially the same straight line as a first electrode stem portion  210 S of a sub-pixel PXn adjacent in the same row (a sub-pixel PXn adjacent, for example, in the first direction DR1). Opposite ends of the first electrode stem portion  210 S in each of the sub-pixels PXn may be spaced apart from opposite ends of the first electrode stem portions  210 S in the other sub-pixels PXn to supply different electrical signals to the first electrode branch portions  210 B, and the first electrode branch portions  210 B may be driven separately. 
     The first electrode branch portion  210 B may branch from at least a portion of the first electrode stem portion  210 S and extend in the second direction DR2, and the branching thereof may end such that the first electrode branch portion  210 B is spaced apart from the second electrode stem portion  220 S facing the first electrode stem portion  210 S. 
     The second electrode  220  may include the second electrode stem portion  220 S extending in the first direction DR1 to face the first electrode stem portion  210 S while being spaced apart from the first electrode stem portion  210 S in the second direction DR2, and the second electrode branch portion  220 B branching from the second electrode stem portion  220 S and extending in the second direction DR2. An end of the second electrode stem portion  220 S may be connected to a second electrode stem portion  220 S of another sub-pixel PXn adjacent in the first direction DR1. That is, the second electrode stem portion  220 S may extend in the first direction DR1 to cross each sub-pixel PXn, unlike the first electrode stem portion  210 S. The second electrode stem  220 S crossing each sub-pixel PXn may be connected to an outer side of the display area DA in which each pixel PX or each sub-pixel PXn is disposed or an extending portion of the non-display area NDA in a certain direction. 
     The second electrode branch portion  220 B may be spaced apart from the first electrode branch portion  210 B to face the first electrode branch portion  210 B, and the second electrode branch portion  220 B may end while being spaced apart from the first electrode stem portion  210 S. The second electrode branch portion  220 B may be connected to the second electrode stem portion  220 S, and an end of the second electrode branch portion  220 B in a direction in which the second electrode branch portion  220 B extends may be located in the sub-pixel PXn while being spaced apart from the first electrode stem portion  210 S. 
     Although in the drawings, a case that two first electrode branch portions  210 B are located in each sub-pixel PXn and one second electrode branch portion  220 B is located between the two first electrode branch portions  210 B is illustrated, embodiments according to the invention are not limited thereto. Alternatively, the first electrode  210  and the second electrode  220  may not necessarily have shapes extending in one direction and may be disposed in various structures. For example, the first electrode  210  and the second electrode  220  may each have a partially curved or bent shape or one of the first and second electrodes  210  and  220  may be arranged to surround the other. A structure or shape in which the first electrode  210  and the second electrode  220  are disposed are not particularly limited, provided at least some regions thereof are spaced apart from each other to face each other so as to form a space therebetween, in which the light-emitting element  300  may be arranged. 
     The first electrode  210  and the second electrode  220  may be electrically connected to a circuit element layer PAL of  FIG. 7  of the display device  10  through contact holes, e.g., through a first electrode contact hole CNTD and a second electrode contact hole CNTS, respectively. In the drawings, a first electrode contact hole CNTD is formed for the first electrode stem portion  210 S of each sub-pixel PXn, and a second electrode contact hole CNTS is formed for only one second electrode stem portion  220 S crossing each sub-pixel PXn. However, embodiments according to the invention are not limited thereto, and second electrode contact holes CNTS may be formed for the sub-pixels PXn in some cases. 
     The plurality of light-emitting elements  300  may be disposed between the first electrode  210  and the second electrode  220 . As shown in the drawings, the plurality of light-emitting elements  300  may be disposed between the first electrode branch portion  210 B and the second electrode branch portion  220 B. One end of each of at least some of the plurality of light-emitting elements  300  may be electrically connected to the first electrode  210  and another end thereof may be electrically connected to the second electrode  220 . The opposite ends of the light-emitting element  300  may be disposed on the first electrode branch portion  210 B and the second electrode branch portion  220 B, respectively, but embodiments according to the invention are not limited thereto. In some cases, the light-emitting element  300  may be disposed between the first electrode  210  and the second electrode  220  such that the opposite ends thereof do not overlap the first electrode  210  and the second electrode  220 . 
     The plurality of light-emitting elements  300  may be disposed between the first and second electrode  210  and  220  to be spaced apart from each other and aligned to be substantially parallel to each other. A gap between the plurality of light-emitting elements  300  is not particularly limited. In some cases, the plurality of light-emitting elements  300  may be arranged adjacent to each other to be clustered together, and a plurality of other light-emitting elements  300  may be clustered together to be spaced a certain distance from each other or may be arranged in different densities while being oriented and aligned in a direction. In an embodiment, the light-emitting element  300  may have a shape extending in one direction, and a direction in which each electrode, e.g., the first electrode branch portion  210 B and the second electrode branch portion  220 B, extends and a direction in which the light-emitting element  300  extends may be substantially perpendicular to each other. However, embodiments according to the invention are not limited thereto, and the light-emitting element  300  may not be perpendicular to the direction in which the first electrode branch portion  210 B and the second electrode branch portion  220 B extend but may be tilted thereto in another embodiment. 
     The display device  10  according to an embodiment may include a first insulating layer  510  covering at least a part of the first electrode  210  and the second electrode  220 , and each sub-pixel PXn may include a first region IR 1  and a second region IR 2  of the first insulating layer  510 , which include materials having different polarities. 
     The first insulating layer  510  may be disposed on each sub-pixel PXn of the display device  10 . The first insulating layer  510  may be disposed to substantially entirely cover each sub-pixel PXn and extend to neighboring sub-pixels PXn. The first insulating layer  510  may be disposed to cover at least a part of the first electrode  210  and the second electrode  220 . Although not shown in  FIG. 2 , the first insulating layer  510  may be disposed to expose part of the first electrode  210  and the second electrode  220 , and particularly, some regions of the first electrode branch portion  210 B and the second electrode branch portion  220 B. This will be described in detail with reference to other drawings below. 
     In the first insulating layer  510 , a region including a hydrophilic material and a region including a hydrophobic material may be formed. The region including the hydrophilic material may be the first region IR 1 , and the region including the hydrophobic material may be the second region IR 2 . As illustrated in  FIG. 2 , the first region IR 1  and the second region IR 2  may be formed in each sub-pixel PXn of the display device  10 . 
     Each of first regions IR 1  may be disposed for one of the sub-pixels PXn. The first regions IR 1  may overlap the first electrode  210  and the second electrode  220  disposed for each sub-pixel PXn. Specifically, the first region IR 1  may be positioned to include the first electrode branch portion  210 B, the second electrode branch portion  220 B, and a region therebetween. A plurality of first regions IR 1  may be formed for the sub-pixels PXn and thus the first regions IR 1  disposed in neighboring sub-pixels PXn may be spaced apart from each other in a direction, e.g., the first direction DR1 or the second direction DR2. That is, the first regions IR 1  may be formed in an island or linear pattern on substantially an entire area of the display device  10 . 
     The second region IR 2  is a region except for the first regions IR 1  and may be formed to surround the first regions IR 1 . The second region IR 2  may be formed to surround the first regions IR 1  and integrally connected to each sub-pixel PXn. In an embodiment, the second regions IR 2  may be located at boundaries of neighboring sub-pixels PXn. The second region IR 2  may be formed at boundaries between sub-pixels adjacent in the first direction DR1, e.g., the first sub-pixel PX 1 , the second sub-pixel PX 2 , and the third sub-pixel PX 3 , to extend in the second direction DR2. Although not shown in the drawings, the second region IR 2  may be formed at boundaries between the first sub-pixel PX 1 , the second sub-pixel PX 2 , and the third sub-pixels PX 3  and sub-pixels PXn adjacent thereto in the second direction DR2 to extend in the first direction DR1. That is, the second regions IR 2  may be formed in a lattice pattern on a substantially entire area of the display device  10 . 
     According to an embodiment, the display device  10  may include first regions IR 1 , each of which is disposed for one of the sub-pixels PXn, and a second region IR 2 , which is a region except for the first regions IR 1 , and the light-emitting elements  300  disposed for the sub-pixels PXn may be disposed in the first regions IR 1 . The first region IR 1  may be located between the first electrode  210  and the second electrode  220 , for example, between the first electrode branch portion  210 B and the second electrode branch portion  220 B. The light-emitting element  300  may be aligned in the first region IR 1  and between the first electrode branch portion  210 B and the second electrode branch portion  220 B. Accordingly, the first region IR 1  may be included in the emission area EMA in which the light-emitting elements  300  are arranged and to which light from the light-emitting elements  300  is emitted. That is, the emission area EMA of each sub-pixel PXn may have a larger area than the first region IR 1 . However, embodiments according to the invention are not limited thereto, and the emission area EMA and the first region IR 1  may have substantially the same area. 
     In an embodiment, the light-emitting elements  300  may be disposed between the first and second electrodes  210  and  220  by spraying ink S of  FIG. 5 , in which the light-emitting elements  300  are dispersed, onto the first and second electrodes  210  and  220  and supplying an alignment signal to the first and second electrodes  210  and  220  during a manufacturing process of the display device  10 . Here, the ink S in which the light-emitting elements  300  are dispersed may be sprayed onto the first insulating layer  510  on the first and second electrodes  210  and  220  and may have liquidity on the first insulating layer  510  and thus move to an adjacent region. The display device  10  according to an embodiment may include a first region IR 1  and a second region IR 2  of the first insulating layer  510 , which include materials having different polarities, and thus, the ink S in which the light-emitting elements  300  are dispersed may be induced to be located in the first region IR 1 . 
     The ink S may form a relatively stronger attractive force with the material included in the first region IR 1  of the first insulating layer  510  than the material included in the second region IR 2  of the first insulating layer  510  and may be sprayed onto the first insulating layer  510  to be provided to the first region IR 1 . As the first region IR 1  is formed between the first electrode  210  and the second electrode  220  in which the light-emitting elements  300  are aligned, the ink S in which the light-emitting elements  300  are dispersed are provided on the first region IR 1  and thus a great part of the light-emitting elements  300  may be aligned between the first electrode  210  and the second electrode  220 . Each pixel PX or sub-pixel PXn of the display device  10  includes the first region IR 1  and the second region IR 2 , and thus, during the manufacturing process of the display device  10 , the ink S in which the light-emitting elements  300  are dispersed may be induced to be moved to a certain region, and the number of light-emitting elements  300  in a region except for the region between the first electrode  210  and the second electrode  220  may be minimized. That is, during the manufacturing process of the display device  10  according to an embodiment, the number of lost light-emitting elements  300  or the number of defective light-emitting elements  300  that are not connected to the electrodes  210  and  220  in each sub-pixel PXn may be minimized. 
     In the manufacturing process of the display device  10 , the ink S in which the light-emitting elements  300  are dispersed may be prevented from flowing to other sub-pixels PXn even when no structure is disposed between adjacent sub-pixels PXn or a structure between adjacent sub-pixels PXn is omitted. The ink S sprayed onto each sub-pixel PXn may be induced to be moved to the first region IR 1  and prevented from flowing to the second region IR 2  from a boundary between the first region IR 1  and the second region IR 2 . The second region IR 2  may be formed at boundaries between sub-pixels PXn, and the ink S sprayed onto one sub-pixel PXn may be prevented from moving beyond a boundary between the sub-pixel PXn and a neighboring sub-pixel PXn. 
     According to an embodiment, the first insulating layer  510  of the display device  10  may include first sub-insulating layers  511  and  512  and a second sub-insulating layer  513 , and the first sub-insulating layers  511  and  512  may include a first portion  511  and a second portion  512 , respectively. A region in which the first portion  511  is located and a region in which the second portion  512  is located may form the first region IR 1  and the second region IR 2  described above, respectively. The first region IR 1  in which the light-emitting elements  300  are disposed may be a region in which the first portion  511  of the first insulating layer  510 , which includes a hydrophilic material, is positioned, and the second region IR 2  may be a region in which the second portion  512  of the first insulating layer  510 , which includes a hydrophobic material is positioned. This will be described in detail with reference to other drawings below. 
       FIG. 3  is a schematic cross-sectional view taken along line X 1 -X 1 ′ of  FIG. 2 .  FIG. 4  is an enlarged view of a portion Q of  FIG. 3 .  FIG. 5  is a schematic diagram illustrating that ink is sprayed on a first insulating layer according to an embodiment.  FIG. 6  is a schematic cross-sectional view taken along line X 2 -X 2 ′ of  FIG. 2 . 
       FIGS. 3 to 6  schematically illustrate a cross section of one sub-pixel PXn and thus a structure of the display device  10  according to an embodiment according to the invention is not limited thereto.  FIGS. 3 to 6  illustrate only a first electrode  210 , a second electrode  220 , a first insulating layer  510 , and light-emitting elements  300 , which are disposed in each sub-pixel PXn, but the display device  10  may further include a plurality of other members. 
     Referring to  FIGS. 3 to 6 , the display device  10  according to an embodiment may include a circuit element layer PAL and an emission layer EML located on the circuit element layer PAL. Structures of these components will be described in detail below. The light-emitting elements  300  are disposed on the emission layer EML. The emission layer EML may include a first electrode  210 , a second electrode  220 , a first insulating layer  510 , and a light-emitting element  300 . The first electrode  210 , the second electrode  220 , and the light-emitting element  300  are as described above. 
     The first insulating layer  510  may be disposed to cover the first electrode  210  and the second electrode  220 , and the light-emitting element  300  may be disposed on the first insulating layer  510  and between the first electrode  210  and the second electrode  220 . In the drawings, opposite ends of the light-emitting element  300  are located at positions overlapping the first electrode  210  and the second electrode  220 , respectively, but embodiments according to the invention are not limited thereto. 
     According to an embodiment, the first insulating layer  510  may include a second sub-insulating layer  513  and a first sub-insulating layers  511  and  512 . The first sub-insulating layers  511  and  512  may include a first portion  511  on a region of the second sub-insulating layer  513 , and a second portion  512  which is a region except for the first portion  511 . The second sub-insulating layer  513  may be located across the first region IR 1  and the second region IR 2  to cover the first electrode  210  and the second electrode  220 . The second sub-insulating layer  513  may be disposed in direct contact with the first electrode  210  and the second electrode  220  and extend to a neighboring sub-pixel PXn. 
     The first portion  511  may be disposed on a region of the second sub-insulating layer  513 . The first portion  511  may be disposed on a part of the first electrode  210  disposed in each sub-pixel PXn and the second electrode  220 . The first portion  511  may be provided only in each sub-pixel PXn. In the drawings, it is illustrated that the first portion  511  overlaps a region of a cross section of the first electrode  210 , i.e., half the first electrode  210 , and covers an entire cross section of the second electrode  220 . That is, the first portion  511  may be provided to overlap only a side of the first electrode  210  facing the second electrode  220  and overlap opposite sides of the second electrode  220  facing the first electrode  210 . However, embodiments according to the invention are not limited thereto, and the first portion  511  may be formed to overlap the entire first electrode  210  or overlap a part of the second electrode  220  in another embodiment. The region in which the first portion  511  is disposed may form a first region IR 1 . A plurality of light-emitting elements  300  may be disposed on the first portion  511  in the first region IR 1 . 
     The second portion  512  may be provided in a region of the second sub-insulating layer  513  in which the first portion  511  is not disposed. The second portion  512  may be disposed on a boundary of a neighboring sub-pixel PXn and may extend to the neighboring sub-pixel PXn to connect one sub-pixel PXn to the neighboring sub-pixel PXn when the second portion  512  is located in one sub-pixel PXn. As illustrated in  FIG. 6 , only the second sub-insulating layer  513  and the second portion  512  may be provided in a region between the first electrode  210  in one sub-pixel PXn and the first electrode  210  in another sub-pixel PXn. The region in which the second portion  512  is provided may form a second region IR 2 , and the light-emitting elements  300  may not be substantially disposed on the second portion  512 . That is, in an embodiment, the density of the light-emitting elements  300  disposed in the first region IR 1  or the first portion  511  may be higher than the density of the light-emitting elements  300  disposed in the second region IR 2  or the second portion  512 . 
     The first portion  511  may include a hydrophilic material, and the second portion  512  may include a hydrophobic material. That is, regions having different polarities may be formed on an upper surface of the first insulating layer  510 . According to an embodiment, during the manufacturing process of the display device  10 , the ink S in which the light-emitting elements  300  are dispersed may be induced to be moved to only a certain region, e.g., the first portion  511  including the hydrophilic material, among the regions having different polarities on the first insulating layer  510 . 
     As shown in  FIG. 5 , in the manufacturing process of the display device  10 , the ink S in which the light-emitting elements  300  are dispersed may be sprayed onto the first electrode  210  and the second electrode  220 . In an embodiment, the first portion  511  forming the first region IR 1  may prevent movement of the ink S to the second portion  512 . The ink S sprayed onto each sub-pixel PXn may be sprayed into the first region IR 1  and maintained at an initial position, and the ink S sprayed into the second region IR 2  other than the first region IR 1  may form a strong attractive force with the first portion  511  including the hydrophilic material and thus be moved into the first region IR 1 . Thus, the number of the light-emitting elements  300  between the first electrode  210  and the second electrode  220  among the light-emitting elements  300  dispersed in the ink S may increase. 
     An ink S spread prevention function of the first insulating layer  510  may be derived by controlling the differences in surface energy between the first and second portions  511  and  512  of the first insulating layer  510  and the ink S. As described above, the first portion  511  may include the hydrophilic material, the second portion  512  may include the hydrophobic material, and the difference in surface energy between the first portion  511  and the ink S may be different from the difference in surface energy between the second portion  512  and the ink S. 
     The ink S sprayed onto the first insulating layer  510  may be in a form appropriate for minimizing surface energy. The ink S may be in a spherical or semi-elliptical form to minimize surface energy. 
     Here, a case in which the ink S is provided on the first portion  511 , i.e., in the first region IR 1 , will be described as an example. The ink S may be provided at a boundary between the first and second portions  511  and  512  to form an interface between the first portion  511  and the ink S and an interface between the ink S and the air. The ink S may have surface energy at the above interfaces and may exhibit behavior for minimizing a value of the surface energy. 
     In an embodiment, for example, when the ink S is positioned on the first portion  511  forming the first region IR 1 , the ink S may have a first force F 1  that moves in a random direction due to the movement of a fluid. The first force F 1  may be a force due to the movement of the fluid contained in the ink S, a force due to gravity acting on the ink S, or a force applied to minimize surface energy of the ink S. The first force F 1  may be applied such that the sum of a level of first surface energy (γSV) between the ink S and the first portion  511  and a level of second surface energy (γSV) between the ink S and the air is minimized. As illustrated in  FIG. 5 , when the level of the first surface energy (γSV) between the ink S and the first portion  511  is smaller than the level of the second surface energy (γSV) between the ink S and the air, the ink S may be moved due to the first force F 1  applied thereto to increase the interface between the ink S and the first portion  511 . 
     When the ink S is positioned between the first region IR 1  and the second region IR 2  and moved to the second region IR 2  by the first force F 1 , a new interface may be formed between the ink S and the second portion  512 . However, when a level of third surface energy (γSV′) formed at the interface between the ink S and the second portion  512  is large, total surface energy of a surface of the ink S may increase. To prevent this problem, a force, i.e., a second force F 2 , applied to minimize the interface between the ink S and the second portion  512  is applied to the ink S. When the second force F 2  applied to the ink S is greater than the first force F 1 , the ink S may not be moved at the boundary between the first portion  511  and the second portion  512 . As described above, in the manufacturing process of the display device  10  according to an embodiment, the ink S in which the light-emitting elements  300  are dispersed may be induced to be positioned in a certain region, for example, the first region IR 1 . That is, the spread of the ink S sprayed onto each sub-pixel PXn to regions other than the first region IR 1  may be prevented. Accordingly, the light-emitting elements  300  dispersed in the ink S may be induced to be positioned only in the first region IR 1  and the number of the light-emitting elements  300  between the electrodes  210  and  220  in the first region IR 1  may be increased. 
     Furthermore, as shown in  FIG. 6 , the second region IR 2  may be formed between different sub-pixels PXn to prevent the spread of the ink S to neighboring sub-pixels PXn even when members that separates sub-pixels PXn from each other are not provided. When different types of light-emitting elements  300  are disposed for sub-pixels PXn, it is necessary to prevent light-emitting elements  300  to be disposed in a specific sub-pixel PXn from being disposed in another sub-pixel PXn in the manufacturing process of the display device  10 . Here, in the display device  10  according to an embodiment, the second region IR 2  may be formed between neighboring sub-pixels PXn so that different types of light-emitting elements  300  may be disposed in the sub-pixels PXn even when an additional member is not provided. 
     According to an embodiment, the first portion  511  may include a hydrophilic material and the second portion  512  may include a hydrophobic material. When the ink S in which the light-emitting elements  300  are dispersed includes a hydrophilic solvent, the second force F 2  applied to the ink S at the boundary between the first portion  511  and the second portion  512  may be greater than the first force F 1  and thus the spread of the ink S into the sub-pixels PXn may be prevented. However, the polarities of the materials included in the first portion  511  and the second portion  512  according to the invention are not limited thereto. In the manufacturing process of the display device  10 , the polarities of the materials included in the first portion  511  and the second portion  512  may be reversed according to the polarity of the ink S in which the light-emitting elements  300  are dispersed. 
     In an embodiment, the first portion  511  may include a material having a contact angle of 30 degrees (°) or less or 5° or less with respect to water, and the second portion  512  may include a material having a contact angle 80° or more or 150° or more with respect to water. When the ink S in which the light-emitting elements  300  are dispersed is hydrophilic, the first portion  511  may also include a hydrophilic material and the second portion  512  may include a hydrophobic material, thereby preventing the spread of the ink S to regions other than the first region IR 1 . However, embodiments according to the invention are not limited thereto, and the polarities of the material of the first portion  511  and the material of the second portion  512  may be opposite to each other as described above in another embodiment. 
     Alternatively, the light-emitting elements  300  may be also provided on a region of each sub-pixel PXn other than the first region IR 1 . In some cases, some light-emitting elements  300  may be provided only on the second region IR 2 . In the display device  10  according to an embodiment, a density of the light-emitting elements  300  disposed in the first region IR 1  may be higher than that of the light-emitting elements  300  disposed on the second region IR 2 . 
     In the manufacturing process of the display device  10 , the above-described structure of the first insulating layer  510  may be obtained by forming the first insulating layer  510  and emitting different types of plasma to the first insulating layer  510  to form the first portion  511 , the second portion  512 , and the second sub-insulating layer  513 . The first portion  511  may be formed by emitting a first plasma (see FIG.  12 ) to the first insulating layer  510 , the second portion  512  may be formed by emitting a second plasma (see  FIG. 14 ) to the first insulating layer  510 , and the second sub-insulating layer  513  may be formed in a region of the first insulating layer  510  to which no plasma is emitted. 
     According to an embodiment, the first insulating layer  510  may include an inorganic insulating material. For example, the first insulating layer  510  may include silicon oxycarbide (SiOCx). The first insulating layer  510  may include silicon oxycarbide and thus contain a silicon-oxygen (Si—O) bond and a silicon-carbon (Si—C) bond. Here, when a plasma is emitted, the silicon-carbon (Si—C) bond may be broken and another bond may be formed by the emitted plasma. In an embodiment, in the manufacturing process of the display device  10 , the first plasma and the second plasma emitted to the first insulating layer  510  may be, respectively, a fluorine (F)-based plasma and an oxygen-based plasma. Accordingly, the first portion  511  may contain a silicon-oxygen (Si—O) bond formed due to the emission of the second plasma and the second portion  512  may contain a silicon-fluoromethyl (Si-CNFM) bond formed by the emission of the first plasma. The second sub-insulating layer  513  may be a region to which the plasmas are not emitted and which includes the same material as the first insulating layer  510 . 
     According to an embodiment, the first insulating layer  510  may include silicon oxycarbide (SiOCx), and thus regions containing different bonds may be formed by plasma emitted to the silicon oxycarbide (SiOCx). That is, the silicon-fluoromethyl (Si-CnFm) bond may be formed by emitting the first plasma to silicon oxycarbide (SiOCx), and the silicon-oxygen (Si—O) bond may be formed by emitting the second plasma. Silicon (Si) contained in silicon oxycarbide (SiOCx) may be broken from a bond regardless of the types of elements of the bond and a new bond may be formed when plasma is emitted to the bond. In other words, an upper surface of the first insulating layer  510  may be surface-modified selectively or reversibly when the first or second plasma is emitted thereto. This will be described below. 
     The first portion  511  may contain a silicon-oxygen (Si—O) bond or a silicon-hydroxide (Si—OH) bond and thus may have hydrophilic polarity and a small contact angle to water. In contrast, the second portion  512  may contain a silicon-fluoromethyl (Si-CNFM) bond and thus may have hydrophobic polarity and a high contact angle to the water. Accordingly, in the manufacturing process of the display device  10 , the ink S sprayed onto the first insulating layer  510  may be induced to be located in the first region IR 1  in which the first portion  511  having the hydrophilic polarity is formed. 
     The first insulating layer  510  may be in a form, in which the first portion  511  and the second portion  51  containing different bonds are formed in some regions by emitting the first or second plasma to substantially one insulating layer. Although in the drawings, the first portion  511 , the second portion  512 , and the second sub-insulating layer  513  are illustrated as different layers, embodiments according to the invention are not limited thereto. The first insulating layer  510  may be formed such that the first portion  511 , the second portion  512 , and the second sub-insulating layer  513  are integrally formed and a composition ratio of materials or the types of bonds may vary according to a position thereof. In some cases, the first insulating layer  510  may include the first portion  511  formed by disposing a layer including a hydrophilic material on the second sub-insulating layer  513  and include the second portion  512  formed by disposing a layer including a hydrophobic material on a region of the second sub-insulating layer  513  except for the first portion  511 . 
     In an embodiment, the first insulating layer  510  may include the second sub-insulating layer  513 , the first portion  511  that is higher in oxygen (O) atom content than the second sub-insulating layer  513 , and the second portion  512  that is higher in fluorine (F) atom content than the second sub-insulating layer  513  and the first portion  511 . Alternatively, the content of oxygen (O) atoms of the first insulating layer  510  in the first region IR 1  may increase from a lower region to an upper region, and the content of fluorine (F) atoms thereof in the second region IR 2  may increase from the lower region to the upper region. The lower region of the first insulating layer  510  may be the second sub-insulating layer  513 . The upper region of the first insulating layer  510 , which is higher in oxygen (O) atom content, in the first region IR 1  may be the first portion  511 , and the upper region of the first insulating layer  510 , which is higher in fluorine (F) atom content, in the second region IR 2  may be the second portion  512 . 
     The first insulating layer  510  according to an embodiment may include silicon oxycarbide (SiOCx), and include the first portion  511 , which is higher in oxygen (O) atom content than other regions, and the second portion  512 , which is higher in fluorine (F) atom content than other regions. Because the first portion  511 , which is higher in oxygen (O) atom content, is hydrophilic and the second portion  512 , which is higher in fluorine (f) atom content, is hydrophobic, the ink S sprayed onto the first insulating layer  510  may be induced to be positioned on a certain region, e.g., the first portion  511 . 
     In some embodiments, a contact electrode  260  of  FIG. 7  may be disposed on the first electrode  210  and the second electrode  220 . The contact electrode  260  may be disposed substantially on the first insulating layer  510 , and at least a portion thereof may be in contact with or electrically connected to the first electrode  210  and the second electrode  220 . 
       FIG. 7  is a cross-sectional view schematically illustrating a partial cross section of a display device according to an embodiment. 
     Referring to  FIG. 7 , a first insulating layer  510  according to an embodiment may be formed to expose at least a portion of a first electrode  210  and a portion of a second electrode  220 , and the display device  10  may further include the contact electrode  260  in contact with the first electrode  210  and the second electrode  220 , which are exposed through an opening. The first insulating layer  510  may be disposed to cover the electrodes  210  and  220 , and the opening may be formed to overlap the electrodes  210  and  220  to expose some regions of the electrodes  210  and  220 . As shown in the drawings, the opening may entirely expose flat top surfaces of the electrodes  210  and  220  and partially expose inclined sides of the electrodes  210  and  220 . However, embodiments according to the invention are not limited thereto. The opening defined in the first insulating layer  510  may expose only part of the upper surfaces of the electrodes  210  and  220 . 
     The contact electrode  260  is disposed on the electrodes  210  and  220 . The contact electrode  260  may be in contact with the regions of the electrodes  210  and  220 , which are exposed through the opening, and at least one end of a light-emitting element  300 . The contact electrode  260  includes a first contact electrode  261  on the first electrode  210  and a second contact electrode  262  on the second electrode  220 . The first contact electrode  261  may be in contact with the exposed region of the first electrode  210  and one end of the light-emitting element  300 , and the second contact electrode  262  may be in contact with the exposed region of the second electrode  220  and another end of the light-emitting element  300 . 
     As shown in  FIG. 7 , the opening of the first insulating layer  510  may expose at least portions of sides of the first and second electrodes  210  and  220 , as well as the upper surfaces thereof. In this case, an area of the electrodes  210  and  220  exposed through the opening may increase and the contact electrode  260  may be in contact with larger regions of the electrodes  210  and  220 . Accordingly, contact resistance between the contact electrode  260  and the electrodes  210  and  220  may decrease. 
     In the manufacturing process of the display device  10 , after forming the first insulating layer  510  covering the entire electrodes  210  and  220 , the light-emitting element  300  may be aligned within a first region IR 1 . Thereafter, the opening for exposing portions of the electrodes  210  and  220  may be formed in the first insulating layer  510 , the contact electrode  260  may be formed in contact with at least one end of the light-emitting element  300  and at least regions of the electrodes  210  and  220 . Even when the electrodes  210  and  220  are entirely covered with the first insulating layer  510 , an electrical signal may be transmitted from the electrodes  210  and  220  to the light-emitting element  300  through the contact electrode  260 , because the display device  10  according to an embodiment further includes the contact electrode  260  in contact with the regions of the electrodes  210  and  20  exposed through the opening and the light-emitting element  300 . 
     In an embodiment, the first contact electrode  261  may be in contact with the first electrode  210  and one end of the light-emitting element  300 , and the second contact electrode  262  may be in contact with the second electrode  220  and another end of the light-emitting element  300 . The light emitting element  300  may be in a form extending in one direction, and opposite ends thereof in the direction may be in contact with the first contact electrode  261  and the second contact electrode  262 , respectively. The contact electrode  260  may be also in contact with a region of sides of the light-emitting element  300  adjacent to opposite ends of the light-emitting element  300 , as well as the opposite ends of the light-emitting element  300 . That is, the contact electrode  260  may be in contact with the light-emitting element  300  to surround the opposite ends of the light-emitting element  300 . However, embodiments according to the invention are not limited thereto. 
     However, the structure of the display device  10  according to the invention is not limited to that illustrated in  FIGS. 3 to 7 , and the display device  10  may have a structure different from that illustrated in  FIGS. 3 to 7  or a larger number of components may be disposed on the circuit element layer PAL in another embodiment. Although not shown in the drawings, the display device  10  may include the circuit element layer PAL below the electrodes  210  and  220 , the second insulating layer  520  of  FIG. 8 , which is disposed to cover at least a portion of the light-emitting element  300 , and the electrodes  210  and  220 , and a passivation layer  550  of  FIG. 8 . The structure of the display device  10  will be described in detail with reference to  FIG. 8  below. 
       FIG. 8  is a cross-sectional view taken along lines Xa-Xa′, Xb-Xb′ and Xc-Xc′ of  FIG. 2 . 
       FIG. 8  illustrates only a cross section of the first sub-pixel PX 1  but may apply to other pixels PX or sub-pixels PXn.  FIG. 8  illustrates a cross section crossing one end and another end of a light-emitting element  300 . 
     Referring to  FIGS. 2 and 8 , the display device  10  may include a circuit element layer PAL and an emission layer EML. The circuit element layer PAL may include a substrate  110 , a buffer layer  115 , a light blocking layer BML, a first transistor  120 , a second transistor  140 , or the like, and the emission layer EML may include a plurality of electrodes  210  and  220 , a light-emitting element  300 , and the plurality of insulating layers  510 ,  520  and  550 , or the like, which are disposed on the first and second transistors  120  and  140 . 
     The substrate  110  may be an insulating substrate. The substrate  110  may be formed of an insulating material such as glass, quartz, or polymer resin. The substrate  110  may be a rigid substrate but may be a flexible substrate capable of being bent, folded or rolled. 
     The light blocking layer BML may be provided on the substrate  110 . The light blocking layer BML may include a first light blocking layer BML 1  and a second light blocking layer BML 2 . The first light blocking layer BML 1  may be electrically connected to a first drain electrode  123  of the first transistor  120  to be described below. The second light blocking layer BML 2  may be electrically connected to a second drain electrode  143  of the second transistor  140 . 
     The first light blocking layer BML 1  and the second light blocking layer BML 2  are disposed to overlap a first active material layer  126  of the first transistor  120  and a second active material layer  146  of the second transistor  140 , respectively. The first and second light blocking layers BML 1  and BML 2  may include a material blocking light and thus prevent light from being incident on the first and second active material layers  126  and  146 . For example, the first and second light blocking layers BML 1  and BML 2  may be formed of an opaque metal material capable of blocking light. However, embodiments according to the invention are not limited thereto, and the light blocking layer BML may be omitted in some cases. 
     The buffer layer  115  is disposed on the light blocking layer BML and the substrate  110 . The buffer layer  115  may be disposed to entirely cover the substrate  110 , including the light blocking layer BML. The buffer layer  115  may prevent the diffusion of impurity ions, prevent the permeation of moisture or external air, and perform a surface planarization function. In addition, the buffer layer  115  may insulate the light blocking layer BML and the first and second active material layers  126  and  146  from one another. 
     A semiconductor layer is disposed on the buffer layer  115 . The semiconductor layer may include the first active material layer  126  of the first transistor  120 , the second active material layer  146  of the second active material layer  146 , and an auxiliary layer  163 . The semiconductor layer may include polycrystalline silicon, monocrystalline silicon, an oxide semiconductor, or the like. 
     The first active material layer  126  may include a first doped region  126   a,  a second doped region  126   b,  and a first channel region  126   c.  The first channel region  126   c  may be disposed between the first doped region  126   a  and the second doped region  126   b.  The second active material layer  146  may include a third doped region  146   a,  a fourth doped region  146   b,  and a second channel region  146   c.  The second channel region  146   c  may be disposed between the third doped region  146   a  and the fourth doped region  146   b.  The first active material layer  126  and the second active material layer  146  may include polycrystalline silicon. The polycrystalline silicon may be formed by crystallizing amorphous silicon. Examples of a method of crystallizing amorphous silicon may include, but are not limited to, a rapid thermal annealing (“RTA”) method, a solid phase crystallization (“SPC”) method, an excimer laser annealing (“ELA”) method, a metal induced crystallization (“MILC”) method, a sequential lateral solidification (“SLS”) method, etc. As another example, the first active material layer  126  and the second active material layer  146  may include monocrystalline silicon, low-temperature polycrystalline silicon, amorphous silicon, or the like. Each of the first doped region  126   a,  the second doped region  126   b,  the third doped region  146   a,  and the fourth doped region  146   b  may be a region of the first or second active material layer  126  or  146 , which is doped with impurities. However, embodiments according to the invention are not limited thereto. 
     A first gate insulating film  150  is disposed on the semiconductor layer. The first gate insulating film  150  may be disposed to cover the entire buffer layer  115 , including the semiconductor layer. The first gate insulating film  150  may function as a gate insulating film of the first and second transistors  120  and  140 . 
     A first conductive layer is disposed on the first gate insulating film  150 . On the first gate insulating film  150 , the first conductive layer may include a first gate electrode  121  on the first active material layer  126  of the first transistor  120 , a second gate electrode  141  on the second active material layer  146  of the second transistor  140 , and a power supply interconnection  161  on the auxiliary layer  163 . The first gate electrode  121  may overlap the first channel region  126   c  of the first active material layer  126 , and the second gate electrode  141  may overlap the second channel region  146   c  of the second active material layer  146 . 
     An interlayer insulating film  170  is disposed on the first conductive layer. The interlayer insulating film  170  may perform a function of an interlayer insulating film. The interlayer insulating film  170  may include an organic insulating material and perform a surface planarization function. 
     A second conductive layer is disposed on the interlayer insulating film  170 . The second conductive layer includes a first drain electrode  123  and a first source electrode  124  of the first transistor  120 , a second drain electrode  143  and a second source electrode  144  of the second transistor  140 , and a power electrode  162  disposed on the power supply interconnection  161 . 
     The first drain electrode  123  and the first source electrode  124  may be in contact with the first doped region  126   a  and the second doped region  126   b  of the first active material layer  126 , respectively, through contact holes passing through the interlayer insulating film  170  and the first gate insulating film  150 . The second drain electrode  143  and the second source electrode  144  may be in contact with the third doped region  146   a  and the fourth doped region  146   b  of the second active material layer  146 , respectively, through the contact holes passing through the interlayer insulating film  170  and the first gate insulating film  150 . The first drain electrode  123  and the second drain electrode  143  may be electrically connected to the first light blocking layer BML 1  and the second light blocking layer BML 2  through another contact hole, respectively. 
     A via layer  200  is disposed on the second conductive layer. The via layer  200  may include an organic insulating material and perform the surface planarization function. 
     A plurality of banks  410  and  420 , a plurality of electrodes  210  and  220 , and a light-emitting element  300  may be disposed on the via layer  200 . 
     The plurality of banks  410  and  420  may be disposed in each sub-pixel PXn to be spaced apart from each other. The plurality of banks  410  and  420  may include a first bank  410  and a second bank  420  disposed adjacent to a central portion of each sub-pixel PXn. 
     The first bank  410  and the second bank  420  are arranged to face each other while being spaced apart from each other. The first electrode  210  may be disposed on the first bank  410 , and the second electrode  220  may be disposed on the second bank  420 . Referring to  FIGS. 2 and 8 , it may be understood that the first electrode branch portion  210 B is disposed on the first bank  410  and the second electrode branch portion  220 B is disposed on the second bank  420 . 
     The first bank  410  and the second bank  420  may be disposed in each sub-pixel PXn to extend in a second direction DR2. Although not shown in the drawings, the first bank  410  and the second bank  420  may extend in the second direction DR2 and thus may extend toward a sub-pixel PXn adjacent in the second direction DR2. However, embodiments according to the invention are not limited thereto, and the first bank  410  and the second bank  420  may be disposed for each sub-pixel PXn to form a pattern on a front surface of the display device  10  in another embodiment. The first bank  410  and the second bank  420  may include polyimide (“PI”) but are not limited thereto. 
     The first bank  410  and the second bank  420  may each have a structure in which at least a portion protrudes with respect to the via layer  200 . The first bank  410  and the second bank  420  may protrude upward with respect to a plane in which the light-emitting element  300  is disposed, and at least part of protruding portions thereof may be inclined. A shape of the protruding portions of the first bank  410  and the second bank  420  is not particularly limited. 
     According to an embodiment, the banks  410  and  420  may not be disposed at a boundary between neighboring sub pixels PXn. For example, a flat surface may be formed between a first sub-pixel PX 1  and a second sub-pixel PX 2  rather than the banks  410  and  420  extending in the second direction DR2. As described above, in each sub-pixel PXn, the first insulating layer  510  including the plurality of sub-insulating layers  511 ,  512 , and  513  may be disposed and the first region IR 1  and the second region IR 2  having different polarities may be defined. In the manufacturing process of the display device  10 , when an organic material or solvent is sprayed onto each sub-pixel PXn by an inkjet printing method, the organic material or solvent may be positioned in the first region IR 1  of each sub-pixel PXn even when the banks  410  and  402  are not disposed at boundaries between sub-pixels PXn. In each sub-pixel PXn, the first insulating layer  510  including the plurality of sub-insulating layers  511 ,  512 , and  513  may be disposed and the sprayed organic material or solvent may be prevented from flowing into adjacent sub-pixels PXn even when the banks  410  and  420  are not provided at the boundaries between neighboring sub-pixels PXn. This is as described in detail with reference to  FIG. 5  above. 
     The plurality of electrodes  210  and  220  may be disposed on the via layer  200  and the banks  410  and  420 . As described above, the electrodes  210  and  220  include the electrode stem portions  210 S and  220 S and the electrode branch portions  210 B and  220 B. In  FIG. 2 , the line Xa-Xa′ cross the first electrode stem portion  210 S, the line Xb-Xb′ crosses the first and second electrode branch portions  210 B and  220 B, and the line XC-XC′ crosses the second electrode stem portion  220 S. That is, it may be understood that the first electrode  210  disposed in a region indicated by the line Xa-Xa′ of  FIG. 8  corresponds to the first electrode stem portion  210 S. The first electrode  210  and the second electrode  220  disposed in a region indicated by the line Xb-Xb′ correspond to the first electrode branch portion  210 B and the second electrode branch portion  220 B, respectively. The second electrode  220  disposed in a region indicated by the line Xc-Xc′ corresponds to the second electrode stem portion  220 S. The electrode stem portions  210 S and  220 S and the electrode branch portions  210 B and  220 B may form the first electrode  210  and the second electrode  220 . 
     Some regions of the first electrode  210  and the second electrode  220  may be provided on the via layer  200 , and some regions thereof may be provided on the first bank  410  and the second bank  420 . As described above, the first electrode stem portion  210 S of the first electrode  210  and the second electrode stem portion  220 S of the second electrode  220  may extend in the first direction DR1, and the first bank  410  and the second bank  420  may extend in the second direction DR2 to be also placed in a sub-pixel PXn adjacent to the second direction DR2. Although not shown in the drawings, the first electrode stem portion  210 S of the first electrode  210  and the second electrode stem portion  220 S of the second electrode  220 , which extend in the first direction DR1, may partially overlap the first and second banks  410  and  420 . However, embodiments according to the invention are not limited thereto, and the first electrode stem portion  210 S and the second electrode stem portion  220 S may not overlap the first bank  410  and the second bank  420  in another embodiment. 
     A first electrode contact hole CNDT may be formed in the first electrode stem portion  210 S of the first electrode  210  to pass through the via layer  200  and partially expose the first drain electrode  123  of the first transistor  120 . The first electrode  210  may be in contact with the first drain electrode  123  through the first electrode contact hole CNTD. The first electrode  210  may be electrically connected to the first drain electrode  123  of the first transistor  120  to receive a certain electrical signal. 
     The second electrode stem portion  220 S of the second electrode  220  may extend in one direction to be placed in a non-emission area in which light-emitting elements  300  are not disposed. A second electrode contact hole CNTS may be formed in the second electrode stem portion  220 S to pass through the via layer  200  and partially expose the power electrode  162 . The second electrode  220  may be in contact with the power electrode  162  via the second electrode contact hole CNTS. The second electrode  220  may be electrically connected to the power electrode  162  to receive a certain electrical signal from the power electrode  162 . 
     Some regions, e.g., the first electrode branch portion  210 B and the second electrode branch portion  220 B, of the first electrode  210  and the second electrode  220  may be located on the first bank  410  and the second bank  420 , respectively. The first electrode branch portion  210 B of the first electrode  210  may be disposed to cover the first bank  410 , and the second electrode portion  220 B of the second electrode  220  may be disposed to cover the second bank  420 . Because the first bank  410  and the second bank  420  are disposed spaced apart from each other with respect to the center of each sub-pixel PXn, the first electrode branch portion  210 B and the second electrode branch portion  220 B may be also spaced apart from each other. A plurality of light-emitting elements  300  may be disposed in a region between the first electrode  210  and the second electrode  220 , i.e., a space between the first electrode branch portion  210 B and the second electrode branch portion  220 B facing each other while being spaced apart from each other. 
     The electrodes  210  and  220  may include a transparent conductive material. For example, the electrode  210  and  220  may include a material such as indium tin oxide (“ITO”), indium zinc oxide (“IZO”) or indium tin-zinc oxide (“ITZO”) but embodiments according to the invention are not limited thereto. In some embodiments, the electrodes  210  and  220  may include a conductive material having high reflectivity. For example, the electrodes  210  and  220  may include a metal, such as silver (Ag), copper (Cu) aluminum (AL), as the material having high reflectivity. 
     In this case, light incident on the electrodes  210  and  220  may be reflected and emitted in an upward direction of each sub-pixel PXn. 
     The electrodes  210  and  220  may be formed by alternately stacking at least one transparent conductive material and at least one metal layer having higher reflectivity or forming a transparent conductive material and a metal layer having higher reflectivity in one layer. In an embodiment, the electrodes  210  and  220  may have a stacked structure of ITO/silver (Ag)/ITO/IZO or may be an alloy containing aluminum (AL), nickel (Ni), lanthanum (LA), etc. However, embodiments according to the invention are not limited thereto. 
     The first insulating layer  510  is disposed on the via layer  200 , the first electrode  210 , and the second electrode  220 . The first insulating layer  510  is disposed to partially cover the first electrode  210  and the second electrode  220 . The first insulating layer  510  is disposed to cover a great part of upper surfaces of the first electrode  210  and the second electrode  220  while partially exposing the first electrode  210  and the second electrode  220 . The first insulating layer  510  may be disposed to expose portions of the upper surfaces of the first and second electrodes  210  and  220 , e.g., portions of an upper surface of the first electrode branch portion  210 B on the first bank  410  and an upper surface of the second electrode branch portion  220 B on the second bank  420 . That is, the first insulating layer  510  may be formed on substantially an entire via layer  200  and include an opening to partially expose the first electrode  210  and the second electrode  220 . The opening of the first insulating layer  510  may be positioned to expose relatively flat upper surfaces of the first electrode  210  and the second electrode  220 . 
     In an embodiment, in the first insulating layer  510 , a flat upper surface may be provided to dispose the light-emitting element  300  between the first electrode  210  and the second electrode  220 . The upper surface may extend in a direction toward the first electrode  210  and the second electrode  220  and end at inclined sides of the first electrode  210  and the second electrode  220 . That is, the first insulating layer  510  may be disposed in a region in which the electrodes  210  and  220  overlap the inclined sides of the first bank  410  and the second bank  420 . The contact electrode  260  described below may be in contact with the exposed regions of the first electrode  210  and the second electrode  220  and may be in smooth contact with an end of the light-emitting element  300  on the flat upper surface of the first insulating layer  510 . 
     However, embodiments according to the invention are not limited thereto. The upper surface of the first insulating layer  510  disposed between the first electrode  210  and the second electrode  220  spaced apart from each other may not be flat but may be stepped. When the light-emitting element  300  is disposed on the first insulating layer  510 , a space may be formed between a lower surface of the light-emitting element  300  and a stepped region of the first insulating layer  510 . The light-emitting element  300  may be disposed to be partially spaced from the upper surface of the first insulating layer  510 , and the space may be filled with a material of the second insulating layer  520  to be described below. 
     The first insulating layer  510  may protect the first electrode  210  and the second electrode  220  while insulating them from each other. In addition, the first insulating layer  510  may prevent the light-emitting element  300  disposed thereon from being damaged due to direct contacted with other members. However, a shape and structure of the first insulating layer  510  according to the invention are not limited thereto. 
     The first insulating layer  510  may include the first portion  511 , the second portion  512 , and the second sub-insulating layer  513  as described above. The second sub-insulating layer  513  may be disposed to cover the first bank  410 , the second bank  420 , the first electrode  210 , and the second electrode  220 , including the via layer  200 . 
     That is, the second sub-insulating layer  513  may be disposed in substantially the same form as the first insulating layer  510 . Although not shown in  FIG. 8 , the first region IR 1  may be formed in a region in which the first portion  511  of the insulating layer  510  is provided and the second region IR 2  may be formed in a remaining region in which the second portion  512  is provided. This is as described above and thus a detailed description thereof will be omitted. 
     The light-emitting element  300  may be disposed on the first insulating layer  510  between the electrodes  210  and  220 . For example, at least one light-emitting element  300  may be disposed on the first insulating layer  510  between the electrode branch portions  210 B and  220 B, i.e., on the first portion  511  forming the first region IR 1 . However, embodiments according to the invention are not limited thereto, and although not shown in the drawings, at least some of the light-emitting elements  300  disposed in each sub-pixel PXn may be disposed in the second region IR 2 . In the display device  10  according to an embodiment, a great part of the light-emitting elements  300  in each sub-pixel PXn may be disposed in the first region IR 1  and only some light-emitting elements  300  may be disposed in the second region IR 2 . 
     Alternatively, some regions of the light-emitting element  300  may be disposed at a position overlapping the electrodes  210  and  220 . Each of the light-emitting elements  300  may be disposed on one of ends of the first and second electrode branch portions  210 B and  220 B facing each other and may be electrically connected to the electrodes  210  and  220  through the contact electrode  260 . 
     The light-emitting element  300  include a plurality of layers disposed in a horizontal direction with respect to the via layer  200 . The light-emitting element  300  of the display device  10  according to an embodiment may include a first semiconductor layer  310 , a second semiconductor layer  320 , and an active layer  330 , which are illustrated in  FIG. 9  and may be sequentially arranged in the horizontal direction with respect to the via layer  200 . As shown in the drawings, the first semiconductor layer  310 , the second semiconductor layer  320 , and the active layer  330  may be sequentially arranged in the light-emitting element  300  in the horizontal direction with respect to the via layer  200 . However, embodiments according to the invention are not limited thereto. An order in which the plurality of layers of the light-emitting element  300  are arranged may be opposite to that described above, and the plurality of layers of the light-emitting element  300  may be arranged in a direction perpendicular to the via layer  200  when the light-emitting element  300  has a different structure in some cases. 
     The second insulating layer  520  may be partially disposed on the light-emitting element  300 . The second insulating layer  520  may be disposed to partially cover an outer surface of the light-emitting element  300 . The second insulating layer  520  may perform a function of fixing the light-emitting element  300  in the manufacturing process of the display device  10  while protecting the light-emitting element  300 . In an embodiment, some materials of the second insulating layer  520  may be disposed between a lower surface of the light-emitting element  300  and the first insulating layer  510 . As described above, the second insulating layer  520  may be formed to fill a space between the first insulating layer  510  and the light-emitting element  300  which is generated in the manufacturing process of the display device  10 . Accordingly, the second insulating layer  520  may be formed to cover the outer surface of the light-emitting element  300 . However, embodiments according to the invention are not limited thereto. 
     The second insulating layer  520  may extend and disposed in the second direction DR2 on a plane between the first electrode branch portion  210 B and the second electrode branch portion  220 B. For example, the second insulating layer  520  may be in an island or linear form on a plane on the via layer  200 . 
     The contact electrode  260  is disposed on the electrodes  210  and  220  and the second insulating layer  520 . The first contact electrode  261  and the second contact electrode  262  may be disposed on the second insulating layer  520  to be spaced apart from each other. The second insulating layer  520  may insulate the first and second contact electrodes  261  and  262  from each other so as not to be in contact with each other. 
     Although not shown in the drawings, a plurality of contact electrodes  260  may extend on a plane in the second direction DR2 to be spaced apart from each other in the first direction DR1. The contact electrode  260  may be in contact with at least one end of the light-emitting element  300  and electrically connected to the first electrode  210  or the second electrode  220  to receive an electrical signal. The contact electrode  260  may include the first contact electrode  261  and the second contact electrode  262 . The first contact electrode  261  may be disposed on the first electrode branch portion  210 B to be in contact with one end of the light-emitting element  300 , and the second contact electrode  262  may be disposed on the second electrode branch portion  220 B to be in contact with another end of the light-emitting element  300 . 
     The first contact electrode  261  may be in contact with an exposed region of the first electrode  210  on the first bank  410 , and the second contact electrode  262  may be in contact with an exposed region of the second electrode  220  on the second bank  420 . The contact electrode  260  may transmit electrical signals transmitted from the electrodes  210  and  220  to the light-emitting element  300 . 
     The contact electrode  260  may include a conductive material. For example, the contact electrode  260  may include ITO, IZO, ITZO, aluminum (AL), or the like. However, embodiments according to the invention are not limited thereto. 
     The passivation layer  550  may be disposed on the first contact electrode  261 , the second contact electrode  262 , and the second insulating layer  520 . The passivation layer  550  may protect the members disposed on the via layer  200  from an external environment. 
     Each of the second insulating layer  520  and the passivation layer  550  described above may include an inorganic or organic insulating material. In an embodiment, the second insulating layer  520  and the passivation layer  550  may include an inorganic insulating layer, such as silicon oxide (SiOx), silicon nitride (SiNx), silicon oxynitride (SiOxNy), aluminum oxide (Al2O3), or aluminum nitride (AlN). The second insulating layer  520  and the passivation layer  550  may include, as an organic insulating material, acrylic resin, epoxy resin, phenol resin, polyamide resin, polyimide resin, unsaturated polyester resin, polyphenylene resin, polyphenylene sulfide resin, benzocyclobutene, cardo resin, siloxane resin, silsesquioxane resin, polymethyl methacrylate, polycarbonate, polymethyl methacrylate-polycarbonate synthetic resin, or the like. However, embodiments according to the invention are not limited thereto. 
     The light-emitting element  300  may be a light-emitting diode, and particularly, an inorganic light-emitting diode formed of an inorganic material. The inorganic light-emitting diode may be aligned between two opposite electrodes having different polarities when an electric field is formed therebetween in a certain direction. The light-emitting element  300  may be aligned between the two opposite electrodes by the electric field formed between the two opposite electrodes. 
     The light-emitting element  300  may be in a form extending in one direction. 
     The light-emitting element  300  may be in the form of a rod, wire, a tube, or the like. In an embodiment, the light-emitting element  300  may have a cylindrical or a rod shape. However, the light-emitting element  300  according to the invention is not limited thereto, and may have various shapes, e.g., a polyprism shape, such as a cube, a rectangular parallelepiped, or a hexagonal prism, or a shape which extends in one direction and the outer side of which is partially inclined in another embodiment. The plurality of semiconductors included in the light-emitting element  300  to be described below may be sequentially arranged or stacked in the direction. 
     The light-emitting element  300  may include semiconductor crystals doped with impurities of a conductive type (e.g., a p-type or n-type). The semiconductor crystals may receive an electrical signal supplied from an external power source and emit light of a specific wavelength band. 
       FIG. 9  is a schematic diagram of a light-emitting element according to an embodiment. 
     A light-emitting element  300  according to an embodiment may emit light of a specific wavelength band. In an embodiment, light emitted from an active layer  330  may be blue light with a central wavelength band of 450 nanometers (nm) to 495 nm. However, it should be understood that the central wavelength band of the blue light according to the invention is not limited thereto and includes all ranges of wavelengths of blue light in the art in another embodiment. The light emitted from the active layer  330  of the light-emitting element  300  according to the invention is not limited thereto, and may be green light of a central wavelength band of 495 nm to 570 nm or red light of a central wavelength band of 620 nm to 750 nm in another embodiment. 
     Referring to  FIG. 9 , the light-emitting element  300  according to an embodiment may include the first semiconductor layer  310 , the second semiconductor layer  320 , the active layer  330 , and an insulating film  380 . The light-emitting element  300  according to an embodiment may further include at least one electrode layer  370 .  FIG. 9  illustrates that the light-emitting element  300  includes one electrode layer  370  but embodiments according to the invention are not limited thereto. In some cases, the light-emitting element  300  may include more than one electrode layer  370  or the electrode layer  370  may be omitted. A description of the light-emitting element  300  below may equally apply even when the number of electrode layers  370  is changed or when the light-emitting element  300  further includes another structure. 
     The first semiconductor layer  310  may be a semiconductor layer of a first conductivity type, e.g., an n type semiconductor. For example, when the light-emitting element  300  emits light of a blue wavelength band, the first semiconductor layer  310  may include a semiconductor material having a chemical formula of Al x Ga y In 1-x-y N (0≤x≤1, 0≤y≤1, 0≤x+y≤1). For example, the first semiconductor layer  310  may include at least one of AlGaInN, GaN, AlGaN, InGaN, AlN, and InN, which is doped with an n type dopant. The first semiconductor layer  310  may be doped with a first conductive type dopant, and the first conductivity type dopant may be, for example, Si, Ge, Sn or the like. In an embodiment, the first semiconductor layer  310  may be N-GaN doped with N-type silicon (Si). A length of the first semiconductor layer  310  may be in a range of 1.5 micrometers (μm) to 5 μm but embodiments according to the invention are not limited thereto. 
     The second semiconductor layer  320  is disposed on the active layer  330  to be described below. The second semiconductor layer  320  may be, for example, a p type semiconductor of a second conductivity type and may include a semiconductor material having a chemical formula of Al x Ga y In 1-x-y N (0≤x≤1, 0≤y≤1, 0≤x+y≤1) when the light-emitting element  300  emits, for example, light of a blue or green wavelength band. For example, the second semiconductor layer  320  may include at least one of AlGaInN, GaN, AlGaN, InGaN, AlN, and InN, which is doped with a p type dopant. The second semiconductor layer  320  may be doped with a second conductive type dopant, and the second conductivity type dopant may be, for example, Mg, Zn, Ca, Se, Ba or the like. In an embodiment, the second semiconductor layer  320  may be P-GaN doped with p-type magnesium (Mg). A length of the second semiconductor layer  320  may be in a range of 0.05 μm to 0.10 μm but embodiments according to the invention are not limited thereto. 
     In the drawings, the first semiconductor layer  310  and the second semiconductor layer  320  are formed in one layer, but embodiments according to the invention are not limited thereto. In some cases, the first semiconductor layer  310  and the second semiconductor layer  320  may further include additional layers, e.g., a clad layer or a tensile strain barrier reducing (“TSBR”) layer, according to the material of the active layer  330 . 
     The active layer  330  is disposed between the first semiconductor layer  310  and the second semiconductor layer  320 . The active layer  330  may include a material of a single or multi-quantum well structure. When the active layer  330  includes the material of the multi-quantum well structure, the active layer  330  may have a structure in which a quantum layer and a well layer are alternately stacked a plurality of times. The active layer  330  may emit light as electron-hole pairs are combined together according to an electrical signal applied through the first semiconductor layer  310  and the second semiconductor layer  320 . For example, when the active layer  330  emits light of the blue wavelength band, the active layer  330  may include a material such as AlGaN, AlGaInN or the like. Particularly, when the active layer  330  has the multi-quantum well structure in which the quantum layer and the well layer are alternately stacked, the quantum layer may include a material such as AlGaN or AlGaInN, and the well layer may include a material such as GaN or AlInN. In an embodiment, the active layer  330  may include AlGaInN as the quantum layer and AlInN as the well layer, and the active layer  330  may emit blue light having a central wavelength band of 450 nm to 495 nm as described above. 
     However, embodiments according to the invention are not limited thereto, and the active layer  330  may have a structure in which a semiconductor material having high band gap energy and semiconductor materials having low band gap energy are alternately stacked, and may include Group III to V semiconductor materials according to a wavelength band of light emitted from the active layer  330  in another embodiment. The light emitted from the active layer  330  is not limited to light of the blue wavelength band, and in some cases, light of a red or green wavelength band may be emitted. A length of the active layer  330  may be in a range of 0.05 μm to 0.10 μm but embodiments according to the invention are not limited thereto. 
     Light may be emitted from the active layer  330  to opposite sides of the light-emitting element  300 , as well as an outer surface thereof in a longitudinal direction. Directionality of the light emitted from the active layer  330  according to the invention is not limited to one direction. 
     The electrode layer  370  may be an ohmic contact electrode. However, the electrode layer  370  according to the invention is not limited thereto and may be a Schottky contact electrode. The electrode layer  370  may include a conductive metal. For example, the electrode layer  370  may include at least one of aluminum (Al), titanium (Ti), indium (In), gold (Au), silver (Ag), indium tin oxide (ITO), indium zinc oxide (IZO), and indium tin-zinc oxide (ITZO). The electrode layer  370  may further include a semiconductor material doped with an n or p type. 
     The insulating film  380  is disposed to surround outer surfaces of the plurality of semiconductors described above. In an embodiment, the insulating film  380  may be disposed to surround at least an outer surface of the active layer  330  and may extend in a direction in which the light-emitting element  300  extends. The insulating film  380  may protect the above-described members. For example, the insulating film  380  may surround sides of the members and expose the opposite ends of the light-emitting element  300  in the longitudinal direction. 
     In the drawings, it is illustrated that the insulating film  380  extends in the longitudinal direction of the light-emitting element  300  to cover ranging from the first semiconductor layer  310  to the electrode layer  370 , but embodiments according to the invention are not limited thereto. The insulating film  380  may cover only the outer surfaces of some conductive type semiconductors, including the active layer  330 , or cover only a part of the outer surface of the electrode layer  370  to partially expose the outer surface of the electrode layer  370  in another embodiment. Alternatively, an upper surface of a cross section of a region of the insulating film  380  adjacent to at least one end of the light-emitting element  300  may have a round shape. 
     A thickness of the insulating film  380  may be in a range of 10 nm to 1.0 μm but embodiments according to the invention are not limited thereto. Preferably, the thickness of the insulating film  380  may be about 40 nm. 
     The insulating film  380  may include materials having an insulating property, for example, silicon oxide (SiOx), silicon nitride (SiOx), silicon oxynitride (SiOxNy), aluminum nitride (AlN), aluminum oxide (Al 2 O 3 ), or the like. Accordingly, it is possible to prevent an electrical short circuit that may occur when the active layer  330  is in direct contact with an electrode that transmits an electrical signal to the light-emitting element  300 . Furthermore, because the insulating film  380  protects the outer surface of the light-emitting element  300 , including the active layer  330 , it is possible to prevent a reduction in luminous efficiency. 
     In some embodiments, the outer surface of the insulating film  380  may be surface-treated. The light-emitting element  300  may be sprayed and aligned onto the electrode during the manufacture of the display device  10  in a state in which the light-emitting element  300  is dispersed in a certain ink. Here, a surface of the insulating film  380  may be hydrophobically or hydrophilically treated so that in the ink, the light-emitting element  300  may be maintained in a dispersed state without being united with other light-emitting elements  300 . 
     A length of the light-emitting element  300  may be in a range of 1 μm to 10 μm or a range of 2 μm to 6 μm, and preferably, a range of 3 μm to 5 μm. A diameter of the light-emitting element  300  be in a range of 300 nm to 700 nm, and an aspect ratio of the light-emitting element  300  may be in a range of 1.2 to 100. However, embodiments according to the invention are not limited thereto, and a plurality of light-emitting elements  300  included in the display device  10  may have different diameters according to the difference between composition rates of the active layer  330 . Preferably, the diameter of the light-emitting element  300  may be about 500 nm. 
     A manufacturing method of a display device  10  according to an embodiment will be described below. 
       FIG. 10  is a flowchart of a manufacturing method of a display device according to an embodiment. 
     According to an embodiment, in the manufacturing process of the display device  10 , the first portion  511  and the second portion  512  of the first insulating layer  510  may be formed through a plasma process. The first portion  511  and the second portion  512  of the first insulating layer  510  may be formed by forming a material of the second sub-insulating layer  513  and processing an upper surface of the second sub-insulating layer  513  using a first or second plasma. The first plasma and the second plasma may be selectively emitted to some regions of each pixel PX or sub-pixel PXn to form the first and second portions  511  and  512  in the regions. 
     After the first insulating layer  510  according to an embodiment is formed by the above process, the light-emitting elements  300  may be disposed in the first region IR 1  in which the first portion  511  is provided, thereby manufacturing the display device  10 . For a more detailed description, other drawings will be referred to. In the following description, only the first electrode  210 , the second electrode  220 , and the first insulating layer  510 , except for the banks  410  and  420  disposed on the circuit element layer PAL, will be shown to describe the manufacturing process of the display device  10 . However, it will be obvious that the following description may also apply to a case in which the first bank  410  and the second bank  420  are disposed on the circuit element layer PAL. 
       FIGS. 11 to 18  are schematic diagrams illustrating a manufacturing process of a display device according to an embodiment. 
     First, as shown in  FIGS. 11 and 12 , a first electrode  210 , a second electrode  220 , and a second sub-insulating layer  513  covering the first and second electrodes  210  and  220  may be formed on a circuit element layer PAL (S 100 ), and an upper surface of the second sub-insulating layer  513  may be processed by a first plasma (S 200 ), thereby forming a first insulating layer  510 ′. The first insulating layer  510 ′ may include a second portion  512  and a second sub-insulating layer  513 . A first portion  511  of the first insulating layer  510 ′ may be further formed in a subsequent process, thereby obtaining a first insulating layer  510 . The first insulating layer  510 ′ may be formed by forming the second sub-insulating layer  513  covering the first electrode  210  and the second electrode  220  and forming a second portion  512  on an upper surface of the second sub-insulating layer  513 . In an embodiment, the second portion  512  may be formed by emitting the first plasma on the second sub-insulating layer  513 . 
     As described above, when the first plasma is emitted to the second sub-insulating layer  513  including silicon oxycarbide (SiOCx), a silicon-carbon (Si-C) bond is broken and a new bond is formed with a gas contained in the first plasma. In an embodiment, the first plasma may be a fluorine-based plasma. Accordingly, the second portion  512  containing a silicon-fluoromethyl (Si-CnFm) bond may be provided on the second sub-insulating layer  513 . 
     Next, referring to  FIGS. 13 and 14 , a first portion  511  is formed by emitting a second plasma to at least some regions of the first insulating layer  510 ′ (S 300 ). In an embodiment, the second plasma may be emitted to a region of an upper surface of the second portion  512 , which is formed by emitting the first plasma between the first electrode  210  and the second electrode  220 . In the region of the upper surface of the second portion  512  to which the second plasma is emitted, the silicon-fluoromethyl (Si-CnFm) bond may be broken and a new bond may be formed with the gas contained in the second plasma. In an embodiment, the second plasma may be an oxygen-based plasma. Accordingly, a first portion  511  containing a silicon-oxygen (Si—O) bond may be formed on the second sub-insulating layer  513 . The region of the second sub-insulating layer  513  on which the first portion  511  is formed may form the first region IR 1 , and the region thereof on which the second portion  512  is formed may form the second region IR 2 . This has been described above. 
     However, embodiments according to the invention are not limited thereto. In some cases, the first portion  511 , the second portion  512 , and the second sub-insulating layer  513  may be formed by emitting the first plasma and the second plasma (see FIG. 
       13 ) on the upper surface of the first insulating layer  510 , respectively, without forming the first insulating layer  510 ′. As will be described below with reference to other drawings, the first plasma and the second plasma may be emitted onto the upper surface of a certain region but may be selectively emitted only to some areas in some cases. Although not shown in the drawings, in some embodiments, a layer including the material of the first insulating layer  510  may be formed, the first portion  511  may be formed by emitting the second plasma to a position corresponding to the first region IR 1 , and the second portion  512  may be formed by emitting the first plasma to a position corresponding to the second region IR 2 . 
     Next, referring to  FIG. 15 , ink S including light-emitting elements  300  is sprayed onto the region processed by the second plasma, i.e., the first portion  511  (S 400 ). In an embodiment, the ink S including the light-emitting elements  300  may be sprayed through a nozzle by an inkjet method. However, embodiments according to the invention are not limited thereto. 
     The ink S may include a solvent and the light-emitting elements  300  dispersed in the solvent. In an embodiment, the ink S may be provided in a solution or a colloid state. For example, the solvent may be, but is not limited to, acetone, water, alcohol, toluene, propylene glycol (“PG”) or propylene glycol methyl acetate (“PGMA”), etc. 
     As described above, the ink S may be induced to be positioned on the first portion  511  in the first region IR 1 , and most of the light-emitting elements  300  may be positioned on the first region IR 1 , i.e., between the first electrode  210  and the second electrode  220 . The ink S may be located only on the first region IR 1  and may not move to the second region IR 2 , and the number of light-emitting elements  300  disposed between the first and second electrodes  210  and  220  may be increased and the number of light-emitting elements  300  that may be lost or remain defective in the manufacturing process of the display device  10  may be reduced. Even when structures are omitted at a boundary of neighboring sub-pixels PXn, the ink S may be prevented from flowing to other sub-pixels PXn. 
     Next, the light-emitting elements  300  are aligned between the first electrode  210  and the second electrode  220  (S 500 ). The aligning of the light-emitting elements  300  (S 500 ) may include supplying an electric signal to the first electrode  210  and the second electrode  220  to form an electric field in the ink S, receiving a dielectrophoretic force through the electric field to dispose the light-emitting elements  300  on the electrodes  210  and  220 , and removing the solvent from the ink S. 
     The light-emitting elements  300  may be disposed on the electrodes  210  and  220  by dielectrophoresis (“DEP”). When the solution in which the light-emitting elements  300  are dispersed is sprayed onto the electrodes  210  and  220  and alternating-current (“AC”) power is supplied to the electrodes  210  and  220 , an electric field may be formed between the first electrode  210  and the second electrode  220  and the dielectrophoretic force may be applied to the light-emitting elements  300  due to the electric field. A force moving or rotating in one direction may be applied to the light-emitting elements  300  receiving the dielectrophoretic force, and finally, the light-emitting elements  300  may be disposed between the first electrode  210  and the second electrode  220 . The ink S may be induced to be positioned in the first region IR 1 , and a plurality of the light-emitting elements  300  may be disposed to be aligned in one direction between the first electrode  210  and the second electrode  220 . 
     Next, as shown in  FIG. 16 , when the light-emitting elements  300  are disposed on the electrodes  210  and  220 , the solvent is removed from the ink S. A general method may be employed to remove the solvent. For example, the solvent may be removed by a method such as heat treatment or infrared irradiation. Thereafter, although not shown in the drawings, the display device  10  according to an embodiment may be manufactured by performing a process of forming a plurality of members to be included in the display device  10 , e.g., a contact electrode  260 , a second insulating layer  520 , a passivation layer  550 , etc. This will be described in detail below. 
     The display device  10  according to an embodiment may include a plurality of sub-pixels PXn, and the manufacturing process of the display device  10  may be performed by sequentially processing the sub-pixels PNx by the second plasma to dispose the light-emitting elements  300 . Here, in a region to which the second plasma is not emitted the second plasma may be blocked by a mask. In an embodiment, generally, the mask may be a mask that does not react with a plasma, and for example, a metal mask, a photoresist (“PR”) or the like may be employed. However, embodiments according to the invention are not limited thereto. 
     Referring to  FIGS. 17 and 18 , according to an embodiment, in the emitting of the second plasma to form the first portion  511 , the mask may be disposed on a region of the first sub-pixel PX 1  except for some regions and the second plasma may be emitted only to the first sub-pixel PX 1 . Accordingly, the first region IR 1  may be formed only between the first electrode  210  and the second electrode  220  disposed in the first sub-pixel PX 1 , and the light-emitting elements  300  sprayed onto the sub-pixels PXn may be located only between the first electrode  210  and the second electrode  220  on the first sub-pixel PX 1 . In the emitting of the second plasma, because the first portion  511  is not formed in the other sub-pixels PXn on which the mask is disposed, the light-emitting elements  300  may be aligned only in the first sub-pixel PX 1 . 
     Next, as shown in  FIG. 18 , when the mask is disposed on the first sub-pixel PX 1  and the second sub-pixel PX 2  in which the light-emitting elements  300  are aligned, the second plasma may be emitted only to a third sub-pixel PX 3 . Thereafter, the light-emitting elements  300  may be aligned on the third sub-pixel PX 3  in the same manner. However, embodiments according to the invention are not limited thereto, and the first plasma and the second plasma may be selectively emitted to some regions as described above. That is, the first region IR 1  and the second region IR 2  of the first sub-pixel PX 1 , the second sub-pixel PX 2 , and the third sub-pixel PX 3  may be formed by emitting the first plasma and the second plasma to some regions in one process. In this case, the light-emitting elements  300  disposed in each sub-pixel PXn may not be sequentially disposed but may be simultaneously disposed in the same process. 
     The method of manufacturing the display device  10  according to an embodiment includes forming the first portion  511  and the second portion  512  having different polarities by emitting a plasma on the second sub-insulating layer  513 , and the ink S sprayed onto each sub-pixel PXn may be induced to be positioned in the first region IR 1 . Accordingly, the number of light-emitting elements  300  disposed between the first electrode  210  and the second electrode  220  may be increased and the number of light-emitting elements  300  that will be lost or remain defective in the manufacturing process of the display device  10  may be reduced. Furthermore, even when a structure at a boundary between neighboring sub-pixels PXn is omitted, the ink S may be prevented from flowing to other sub-pixels PXn. 
     Various embodiments of the display device  10  will be described further with reference to other drawings below. 
       FIGS. 19 and 20  are plan views illustrating sub-pixels of display devices according to other embodiments. 
     A first region IR 1  according to an embodiment may not necessarily be limited to the shape shown in  FIG. 2 . In some cases, the first region IR 1  may be provided by forming a plurality of patterns in one sub-pixel PXn. 
     Referring to  FIGS. 19 and 20 , in display devices  10 _ 1  and  10 _ 2  according to embodiments, a plurality of first regions IR 1 _ 1  or IR 1 _ 2  may be disposed in one sub-pixel PXn to be spaced apart from each other. The plurality of first regions IR 1 _ 1  or IR 1 _ 2  illustrated in  FIGS. 19 and 20  may be understood as regions in which the first portion  511  of the first insulating layer  510  is substantially formed. The display devices  10 _ 1  and  10 _ 2  of  FIGS. 19 and 20  are the same as the display device  10  of  FIG. 2  except that the plurality of first regions IR 1 _ 1  and IR 1 _ 2  are spaced apart from each other. A form in which the first regions IR 1 _ 1  and IR 1 _ 2  are disposed will now be described in detail and parts that are the same as those described above will be omitted. 
     First, in the display device  10 _ 1  of  FIG. 19 , two first regions IR 1 _ 1  extending in one direction, i.e., a second direction DR2, may be disposed to be spaced apart from each other in one sub-pixel PXn. The plurality of first regions IR 1 _ 1  may be disposed between one first electrode branch portion  210 B and a second electrode branch portion  220 B or between the second electrode branch portion  220 B and another first electrode branch portion  210 B. Each of the plurality of first regions IR 1 _ 1  may be in a form extending in the second direction DR2, along the first electrode branch portion  210 B and the second electrode branch portion  220 B. The plurality of first regions IR 1 _ 1  may be spaced apart from each other in the first direction DR1 on the second electrode branch portion  220 B. 
     Next, in the display device  10 _ 2  of  FIG. 20 , a plurality of first regions IR 1 _ 2  may be disposed in one sub-pixel PXn to be spaced apart from each other in the first direction DR1 and the second direction DR2. The display device  10 _ 2  of  FIG. 20  is the same as the display device  10 _ 1  of  FIG. 19  except that more than two first regions IR 1 _ 2  are disposed in each sub-pixel PXn to be spaced apart from each other in the first direction DR1 and the second direction DR2. 
     As described above, the first regions IR 1 _ 1  and IR 1 _ 2  of the display devices  10 _ 1  and  10 _ 2  may be regions in which the first portion  511  of the first insulating layer  510  is formed, and the first portion  511  may be formed by emitting the second plasma. In the emitting of the second plasma, the second plasma may be partially emitted to each sub-pixel PXn by placing a mask thereon. According to an embodiment, the first portion  511  may be partially formed in one sub-pixel PXn by partially emitting the second plasma. Accordingly, light-emitting elements  300  may be intensively disposed in a specific region of each sub-pixel PXn. 
       FIG. 21  is a plan view of a sub-pixel of a display device according to another embodiment.  FIG. 22  is a cross-sectional view schematically illustrating a cross section of a sub-pixel of the display device of  FIG. 21 . 
     Referring to  FIGS. 21 and 22 , a display device  10 _ 3  according to an embodiment may include larger numbers of first electrode branch portions  210 B_ 3  and second electrode branch portions  220 B_ 3  than the numbers of the first electrode branch portions  210 B and second electrode branch portions  220 B in  FIG. 2 .  FIGS. 21 and 22  illustrate that a first electrode  210 _ 3  includes three first electrode branch portions  210 B_ 3  and a second electrode  220 _ 3  includes two second electrode branch portions  220 B_ 3 . The display device  10 _ 3  of  FIGS. 21 and 22  is the same as the display device  10  of  FIG. 2  except that larger numbers of electrode branch portions  210 B_ 3  and  220 B_ 3  are provided. Hereinafter, redundant description will be omitted and differences will be described. 
     The display device  10 _ 3  of  FIGS. 21 and 22  includes a plurality of first electrode branch portions  210 B_ 3  and a plurality of second electrode branch portions  220 B_ 3  and thus a region of one sub-pixel PXn in which light-emitting elements  300  may be disposed may increase. Accordingly, more light-emitting elements  300  may be disposed in one sub-pixel PXn and the amount of light emitted from each sub-pixel PXn may be increased compared to the embodiment in  FIG. 2 . In addition, the area where the first portion  511 _ 3  of each sub-pixel PXn is formed can also be increased. 
     Unlike the display device  10  of  FIG. 2 , in the display device  10 _ 3  of  FIGS. 21 and 22 , the first portion  511 _ 3  may be provided to overlap opposite sides of a certain first electrode branch portions  210 B_ 3  which faces second electrode branch portions  220 B_ 3  in its opposite sides (e.g., the center first electrode branch portions  210 B_ 3  of the three first electrode branch portions  210 B_ 3 ). 
       FIG. 23  is a plan view of a sub-pixel of a display device according to another embodiment.  FIG. 24  is a cross-sectional view schematically illustrating a cross section of a sub-pixel of the display device of  FIG. 23 . 
     Referring to  FIGS. 23 and 24 , a display device  10 _ 4  according to an embodiment may include a smaller number of first electrode branch portions  210 B_ 4 . 
     In  FIGS. 23 and 24 , the first electrode  210 _ 4  includes one first electrode branch portion  210 B_ 4 , and the second electrode  220 _ 4  includes one second electrode branch portion  220 B_ 4 . The display device  10 _ 4  of  FIGS. 23 and 24  is the same as the display device  10  of  FIG. 2  except that a smaller number of electrode branch portions  210 B_ 4  and  220 B_ 4  are provided. Hereinafter, redundant description will be omitted and differences will be described. 
     The display device  10 _ 4  of  FIGS. 23 and 24  may include only one first electrode branch portion  210 B_ 4  and one second electrode branch portion  220 B_ 4 . In this case, a first portion  511 _ 4  may be disposed to overlap only one side of the first electrode branch portion  210 B_ 4  and one side of the second electrode branch portion  220 B_ 4  facing each other. Furthermore, the display device  10 _ 4  may include only one first electrode branch portion  210 B_ 4  and one second electrode branch portion  220 B_ 4 , thereby reducing the size of each sub-pixel PXn. Because a first region IR 1 _ 4  may be formed for each sub-pixel PXn to dispose light-emitting elements  300  at a high density in a certain region, a desired number of light-emitting elements  300  may be disposed even when the size of one sub-pixel PXn is reduced. In addition, as the size of one sub-pixel PXn is reduced, a size of one pixel PX including three sub-pixels PXn may decrease. In this case, a second region IR 2 _ 4  at a boundary between neighboring sub-pixels PXn may effectively prevent ink S from flowing to other sub-pixels PXn when light-emitting elements  300  are aligned in one sub-pixel PXn. 
     In an embodiment, each sub-pixel PXn may include different types of light-emitting elements  300  to emit light of different wavelength bands. 
       FIG. 25  is a plan view illustrating three sub-pixels of the display device of  FIG. 23 .  FIGS. 26 to 28  are schematic cross-sectional views illustrating some operations of a manufacturing process of the display device of  FIG. 25 . 
     Referring to  FIGS. 25 to 28 , in a display device  10 _ 5  according to an embodiment, a first sub-pixel PX 1 , a second sub-pixel PX 2 , and a third sub-pixel PX 3  may include first light-emitting elements  301 _ 5 , second light-emitting elements  302 _ 5 , and third light-emitting elements  303 _ 5 , respectively, which are different from one another. As each sub-pixel PXn includes one first electrode branch portion  210 B_ 5  and one second electrode branch portion  220 B_ 5 , a boundary between neighboring sub-pixels PXn may decrease significantly. Further, as each of the sub-pixels PXn includes different light emitting elements  300 _ 5 , it is important to prevent ink S sprayed onto electrodes from flowing to neighboring sub-pixels PXn during a manufacturing process of the display device  10 _ 5 . The display device  10 _ 5  according to an embodiment includes a first region IR 1 _ 5  and a second region IR 2 _ 5  to effectively prevent ink S including light-emitting elements  300 _ 5  from flowing to neighboring sub-pixels PXn when the ink S is sprayed. 
     As shown in  FIGS. 26 to 28 , a first insulating layer  510 _ 5  may include silicon oxycarbide, and a first portion  511 _ 5  and a second portion  512 _ 5  may be formed by plasmas emitted to the first insulating layer  510 _ 5 . Particularly, even when the second plasma is emitted to the second portion  512 _ 5 , the first portion  511 _ 5  may be formed. Accordingly, the first portion  511 _ 5  may be formed by emitting the second plasma to a first sub-pixel PX 1 , the first light-emitting element  301 _ 5  may be disposed, and the second portion  512 _ 5  may be formed in a region, except for a region in which the first light-emitting element  301 _ 5  overlaps the first light-emitting element  301 _ 5 , by emitting the second plasma (as shown in  FIG. 27 ). 
     According to an embodiment, a first region IR 1 _ 5  may be selectively formed in a certain region by repeatedly performing a process of forming the first portion  511 _ 5  by emitting the second plasma to the region and a process of forming the second portion  512 _ 5  by emitting the first plasma to the region. The ink S in which the light-emitting elements  300 _ 5  are dispersed may not flow to a second region IR 2 _ 5  except for the first region IR 1 _ 5  but may be positioned only on the first region IR 1 _ 5 . Thus, when the different light-emitting elements  300 _ 5  are disposed in a relatively narrow pixel PX or sub-pixel PXn, a light-emitting element  300 _ 5 , e.g., the first light-emitting element  301 _ 5 , may be prevented from being disposed in a second sub-pixel PX 2  or a third sub-pixel PX 3  other than the first sub-pixel PX 1  even when a separate structure at a boundary between sub-pixels PXn is omitted. 
     A structure of the light-emitting element  300  according to the invention is not limited to that illustrated in  FIG. 9 , and the light-emitting element  300  may have a different structure. 
       FIG. 29  is a schematic diagram of a light-emitting element according to another embodiment. 
     Referring to  FIG. 29 , a light-emitting element  300 ′ may have a shape which extends in one direction and sides of which are partially inclined. That is, the light-emitting element  300 ′ according to an embodiment may have a partially conical shape. 
     The light-emitting element  300 ′ may be formed such that a plurality of layers are not stacked in one direction but may each be formed to surround an outer surface of another layer. The light-emitting element  300 ′ of  FIG. 29  is the same as the light-emitting element  300  of  FIG. 9  except that the shapes of the layers are slightly different. A description of parts that are the same as those of the light-emitting element  300  will be omitted and differences from the light-emitting element  300  will be described below. 
     According to an embodiment, a first semiconductor layer  310 ′ may extend in one direction and opposite ends thereof may be inclined toward a center thereof. The first semiconductor layer  310 ′ of  FIG. 29  may include a main body having a rod or cylindrical shape and upper and lower ends each having a conical shape. A degree of inclination of the upper end of the main body may be higher than that of inclination of the lower end thereof. 
     An active layer  330 ′ is disposed to surround an outer surface of the main body of the first semiconductor layer  310 ′. The active layer  330 ′ may have a ring shape extending in one direction. The active layer  330 ′ may not be formed on the upper end and the lower end of the first semiconductor layer  310 ′. That is, the active layer  330 ′ may be in contact with only parallel sides of the first semiconductor layer  310 ′. 
     A second semiconductor layer  320 ′ is disposed to surround an outer surface of the active layer  330 ′ and the upper end of the first semiconductor layer  310 ′. The second semiconductor layer  320 ′ may include a main body having a ring shape and an upper end, the sides of which are inclined. That is, the second semiconductor layer  320 ′ may be in direct contact with the parallel sides of the active layer  330 ′ and the inclined upper end of the first semiconductor layer  310 ′. However, the second semiconductor layer  320 ′ is not formed on the lower end of the first semiconductor layer  310 ′. 
     An electrode layer  370 ′ is disposed to surround an outer surface of the second semiconductor layer  320 ′. That is, a shape of the electrode layer  370 ′ may be substantially the same as that of the second semiconductor layer  320 ′. That is, the electrode layer  370 ′ may be in contact with the entire outer surface of the second semiconductor layer  320 ′. 
     An insulating film  380 ′ may be disposed to surround the outer sides of the electrode layer  370 ′ and the first semiconductor layer  310 ′. The insulating film  380 ′ may be in direct contact with the lower end of the first semiconductor layer  310 ′ and exposed lower ends of the active layer  330 ′ and the second semiconductor layer  320 ′, including the electrode layer  370 ′. 
     In concluding the detailed description, those skilled in the art will appreciate that many variations and modifications can be made to the preferred embodiments without substantially departing from the principles of the invention. Therefore, the disclosed preferred embodiments of the invention are used in a generic and descriptive sense only and not for purposes of limitation.