Abstract:
Methods of forming a semiconductor device include forming a mask layer on a semiconductor substrate. The mask layer has vertically and horizontally extending portions. The vertically extending portions have a thickness selected to provide a desired line width to an underlying structure to be formed using the mask layer and a height greater than a height of the horizontally extending portions. The underlying structure is formed using the mask layer.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is related to and claims priority under 35 U.S.C. §119 of Korean Patent Application No. 2007-24097, filed on Mar. 12, 2007, the entire contents of which are hereby incorporated by reference. 
       BACKGROUND OF THE INVENTION 
       [0002]    The present invention relates to methods of forming a semiconductor device, and more particularly, to methods of forming a semiconductor device including a fine pattern. 
         [0003]    A semiconductor (integrated circuit) device generally includes a variety of types of patterns that are disposed on a semiconductor substrate and are electrically connected to each other to operate in a desired manner. Conventionally, the semiconductor patterns are generally defined using an exposure process. In such a process, a photoresist pattern is generally formed including openings at locations selected so that the exposure process defines the semiconductor pattern as a layer on the semiconductor substrate. 
         [0004]    In a high integration semiconductor device, a line width (spacing between feature lines) that the exposure process may define has a limit. Particularly, a number of problems due to the exposure process may occur in light of semiconductor industry standards that requires a minimum line width of several tens of a nanometer. For instance, when a semiconductor pattern is defined using the exposure process, a uniformity of a line width of the semiconductor pattern may be degraded by a wafer region, a uniformity of exposure light and/or a uniformity of a lower portion layer. That is, a distribution of a line width of the semiconductor pattern may increase. As the integration density of semiconductor devices increase, a uniformity of a line width of the semiconductor pattern may be more severely degraded. Characteristics of the unit devices formed by the semiconductor pattern may become different (vary) due to the variation of the line width, which may cause a malfunction of the semiconductor device. For example, the variation of the line width may have a serious effect on a high integration memory device, where the same patterns are repeatedly arranged. 
         [0005]    It may be more difficult to define a space between patterns having a fine line width than a pattern having a fine line width using the exposure process. To address this problem, a double exposure process has been introduced. In the typical double exposure process, first mask patterns of a large space are formed by a first exposure process and second mask patterns of a large space are formed between the first mask patterns by a second exposure process. However, the double exposure process may have a problem of a misalignment between the first and second mask patterns. 
       SUMMARY OF THE INVENTION 
       [0006]    In some embodiments, methods of forming a semiconductor device include forming a mask layer on a semiconductor substrate. The mask layer has vertically and horizontally extending portions. The vertically extending portions have a thickness selected to provide a desired line width to an underlying structure to be formed using the mask layer and a height greater than a height of the horizontally extending portions. The underlying structure is formed using the mask layer. 
         [0007]    In other embodiments, the underlying structure is mask patterns. The semiconductor device may be a memory device and forming the underlying structure further includes forming word lines using the mask patterns. Forming the mask patterns may include concurrently forming a string selection mask pattern, a ground selection mask pattern and a plurality of cell mask patterns extending between the string selection mask pattern and the ground selection mask pattern. The string selection mask pattern and the ground selection mask pattern may have a line width greater than a line width of the cell mask patterns. Forming the word lines may include forming the word lines using the cell mask patterns and forming the underlying structure may further include forming a string selection line using the string selection mask pattern and forming a ground selection line using the ground selection mask pattern. 
         [0008]    In further embodiments, methods of forming a semiconductor device include forming a plurality of first guide patterns on an etching target layer of a substrate and conformally forming a mask layer on the substrate in a region including the first guide patterns to define empty regions on respective sides of the first guide patterns. Second guide patterns are formed in the empty regions. The mask layer is planarized down to expose the first guide pattern and to define a preliminary mask pattern including wall portions between the first and second guide patterns and a base portion under the second guide pattern. The first and second guide patterns are removed and the base portion is removed by anisotropic etching of the mask layer to form mask patterns. 
         [0009]    In other embodiments, removing the first and second guide patterns is preceded by removing a guide pattern selected from the first and second guide patterns to form a gap region and forming a filling mask pattern that fills the gap region. The filling mask pattern is formed of a material having an etching selectivity with respect to the first and second guide patterns. The mask patterns may include a first mask pattern and a second mask pattern displaced therefrom, the first mask pattern being the anisotropically etched wall portion and the second mask pattern including the filling mask pattern and a pair of the anisotropically etched wall portions in contact with both sidewalls of the filling mask pattern. The filling mask pattern and the mask layer may be formed of a same material. The first guide patterns may be formed to be parallel to each other. 
         [0010]    In further embodiments, the methods further include etching the etching target layer to form actual patterns using the mask patterns as an etching mask. The etching target layer may be formed of a conductive material. The etching target layer may be a hard mask layer and the actual patterns correspond to hard mask patterns and the methods may further include etching the substrate using the hard mask pattern as an etching mask to form a trench defining an active region. The first and second guide patterns may be formed of a same material. 
         [0011]    In yet other embodiments, methods of forming a semiconductor device include forming first guide patterns on a control gate conductive layer of a substrate. The first guide patterns extend parallel to each other. The first guide patterns include a string selection guide pattern, a ground selection guide pattern, and a plurality of cell guide patterns between the string and ground selection guide patterns. A mask layer is conformally formed on the substrate in a region including the first guide patterns to define empty regions on respective sides of the first guide patterns. Second guide patterns are formed in the empty regions. The mask layer is planarized down to a top surface of the first guide pattern to form preliminary mask patterns. Each of the preliminary mask patterns includes a wall portion between the first and second guide patterns and a base portion under the second guide pattern. The string and ground selection guide patterns are removed to form respective first and second gap regions. First and second filling mask patterns are formed that fill the respective first and second gap regions. The first and second guide patterns are removed and the base portion is removed by anisotropic etching to form mask patterns. The mask layer and the first and second filling mask patterns are formed of a material having an etching selectivity with respect to the first and second guide patterns. 
         [0012]    In other embodiments, the mask pattern includes a string selection mask pattern, cell mask patterns and a ground selection mask pattern. The string selection mask pattern includes the first filling mask pattern and the anisotropically etched wall portions in contact with both sides of the first filling mask pattern. The ground selection mask pattern includes the second filling mask pattern and the anisotropically etched wall portions in contact with both sides of the second filling mask pattern. The cell mask patterns include the anisotropically etched wall portions between the string selection mask pattern and the ground selection mask pattern. 
         [0013]    In further embodiments, removing the base portion is followed by etching the control gate conductive layer to form a string selection line, word lines and a ground selection line using the mask patterns as an etching mask. Etching the control gate conductive layer may be followed by implanting dopant ions into the substrate using the string selection line, word lines and the ground selection line as a mask to form a common source region, cell source/drain regions and a common drain region. 
         [0014]    In other embodiments, forming first guide patterns is preceded by forming a tunnel insulating layer on the substrate, forming a charge storage layer on the tunnel insulating layer and forming a blocking insulating layer on the charge storing layer. The control gate conductive layer is formed on the blocking insulating layer. The charge storage layer may be formed of an insulating material including deep level traps and the string selection line, the word lines and the ground selection line may be formed by etching the control gate conductive layer using the mask patterns as an etching mask. The charge storage layer may be formed of polysilicon and the string selection line, the word lines and the ground selection line may be formed by successively etching the control gate conductive layer, the blocking insulating layer and the charge storage layer using the mask patterns as an etching mask. One of the word lines closest to the string selection line and one of the word lines closest to the ground selection line may be dummy lines that are not coupled to active cells. 
         [0015]    In further embodiments, the mask layer, the first filling mask pattern and second filling mask pattern are formed of a same material. The first and second guide patterns may be formed of a same material. The wall portions between the string selection guide and the ground selection pattern may be an even number of wall portions. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0016]    The above and other aspects, features and advantages of the present invention will be more apparent from the following detailed description taken in conjunction with the accompanying drawings, in which: 
           [0017]      FIGS. 1A through 1J  are cross sectional views illustrating a method of forming a semiconductor device in accordance with some embodiments of the present invention. 
           [0018]      FIG. 2  is a top plan view seen from a direction A shown in  FIG. 1A . 
           [0019]      FIGS. 3A through 3G  are cross sectional views illustrating a method of forming a semiconductor device in accordance with further embodiments of the present invention. 
           [0020]      FIG. 4  is a top plan view seen from a direction B shown in  FIG. 3A . 
           [0021]      FIG. 5  is a top plan view seen from a direction C shown in  FIG. 3G . 
       
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
       [0022]    The present invention is described more fully hereinafter with reference to the accompanying drawings, in which embodiments of the invention are shown. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. In the drawings, the sizes and relative sizes of layers and regions may be exaggerated for clarity. 
         [0023]    It will be understood that when an element or layer is referred to as being “on,” “connected to” or “coupled to” another element or layer, it can be directly on, connected or coupled to the other element or layer or intervening elements or layers may be present. In contrast, when an element is referred to as being “directly on,” “directly connected to” or “directly coupled to” another element or layer, there are no intervening elements or layers present. Like reference numerals refer to like elements throughout. As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items. 
         [0024]    It will be understood that, although the terms first, second, etc. may be used herein to describe various elements, components, regions, layers and/or sections, these elements, components, regions, layers and/or sections should not be limited by these terms. These terms are only used to distinguish one element, component, region, layer or section from another region, layer or section. Thus, a first element, component, region, layer or section discussed below could be termed a second element, component, region, layer or section without departing from the teachings of the present invention. 
         [0025]    Spatially relative terms, such as “beneath,” “below,” “lower,” “above,” “upper” and the like, may be used herein for ease of description to describe one element or feature&#39;s relationship to another element(s) or feature(s) as illustrated in the figures. It will be understood that the spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. For example, if the device in the figures is turned over, elements described as “below” or “beneath” other elements or features would then be oriented “above” the other elements or features. Thus, the exemplary term “below” can encompass both an orientation of above and below. The device may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein interpreted accordingly. 
         [0026]    The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the singular forms “a,” “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises” and/or “comprising,” when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. 
         [0027]    Embodiments of the present invention are described herein with reference to cross-section illustrations that are schematic illustrations of idealized embodiments (and intermediate structures) of the present invention. As such, variations from the shapes of the illustrations as a result, for example, of manufacturing techniques and/or tolerances, are to be expected. Thus, embodiments of the present invention should not be construed as limited to the particular shapes of regions illustrated herein but are to include deviations in shapes that result, for example, from manufacturing. For example, an implanted region illustrated as a rectangle will, typically, have rounded or curved features and/or a gradient of implant concentration at its edges rather than a binary change from implanted to non-implanted region. Likewise, a buried region formed by implantation may result in some implantation in the region between the buried region and the surface through which the implantation takes place. Thus, the regions illustrated in the figures are schematic in nature and their shapes are not intended to illustrate the actual shape of a region of a device and are not intended to limit the scope of the present invention. 
         [0028]    Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the present invention belongs. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and this specification and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein. 
         [0029]    Embodiments of the present invention will now be further described with reference to the figures.  FIGS. 1A through 1J  are cross sectional views illustrating a method of forming a semiconductor device in accordance with some embodiments of the present invention and  FIG. 2  is a top plan view seen from a direction A shown in  FIG. 1A . 
         [0030]    Referring to  FIGS. 1A and 2 , first guide patterns  115  are formed on an etching target layer  110  of a semiconductor (integrated circuit) substrate  100 . A first guide layer may be formed on the etching target layer  110  and the first guide patterns  115  may be formed by patterning the first guide layer. The process of patterning the first guide layer may include a lithography process. The first guide patterns  115  may extend in one common direction to be parallel with each other as shown in  FIG. 2 . The first guide patterns  115  are spaced apart from each other. The first guide patterns  115  may be formed to have the same interval from each other. In some embodiments, at least portions of the first guide patterns  115  may be formed to have a different interval from each other (i.e., variations in spacing therebetween). 
         [0031]    The etching target layer  110  may be formed of conductive material. In some embodiments, the etching target layer  110  may be formed of a hard mask layer that includes a material having an etching selectivity with respect to the substrate  100 . When the etching target layer  110  is formed of the hard mask layer, the etching target layer  110  may include an oxide layer and/or a nitride layer that are sequentially stacked. The first guide patterns  115  may be formed of a material having an etching selectivity with respect to the etching target layer  110 . 
         [0032]    Referring to  FIG. 1B , a mask layer  120  is shown conformally formed on an entire surface of the substrate  100  including the first guide patterns  115 . The mask layer  120  is shown formed to have a substantially uniform thickness (conformally) along a sidewall and a top surface of the first guide pattern  115  and along a surface of the etching target layer  110  between the first guide patterns  115 . Thus, an empty region  125  is formed between the adjacent first guide patterns  115 . That is, the empty region  125  is formed at both sides of the first guide patterns  115 . A sidewall and a bottom surface of the empty region  125  are formed of the mask layer  120 . That is, the empty region  125  is surrounded by the mask layer  120  and a top portion of the empty region  125  is opened. The empty region  125  may be formed to have a groove shape that extends in parallel with the first guide patterns  115 . 
         [0033]    The mask layer  120  may be formed by a chemical vapor deposition (CVD) process and/or an atomic layer deposition (ALD) process. In some embodiments, the mask layer  120  is beneficially formed by an atomic layer deposition (ALD) process that forms the mask layer  120  on the sidewall of the first guide patterns  115  with a sufficient and substantially uniform thickness. 
         [0034]    The mask layer  120  may be formed of material having an etching selectivity with respect to the first guide patterns  115 . Also, the mask layer  120  may be formed of material having an etching selectivity with respect to the etching target layer  110 . 
         [0035]    Referring to  FIG. 1C , second guide patterns  130  and  130   a  are formed in the empty region  125 , respectively. A method of forming the second guide patterns  130  and  130   a  will now be described. First, a second guide layer is formed on an entire surface of the substrate  100  to fill the empty regions  125 . Subsequently, the second guide layer is planarized down to the top surface of the mask layer  120 . Accordingly, the second guide patterns  130  and  130   a  may be formed to fill the empty regions  125 , respectively. After the second guide layer is planarized, top surfaces of the second guide patterns  130  and  130   a  may be recessed to have the substantially same height as top surfaces of the first guide patterns  115 .  FIG. 1C  is a cross sectional view illustrating the recessed second guide patterns  130  and  130   a.  The planarization process of the second guide layer and the recessed process may be sequentially performed by wet etching. In some embodiments, the planarization process of the second guide layer is performed by a chemical mechanical polishing (CMP) process and/or an etch-back process, and the process to recess the second guide layer may be performed using wet etching. In further embodiments, the planarization process of the second guide layer and the recessing process may be sequentially performed using an etch-back process. 
         [0036]    The second guide patterns  130  and  130   a  may be formed of a material having an etching selectivity with respect to the mask layer  120 . That is, the mask layer may be formed of material having an etching selectivity with respect to the first and second guide patterns  115 ,  130  and  130   a,  and with respect to the etching target layer  110 . The second guide patterns  130  and  130   a  may have an etching selectivity with respect to the etching target layer  110 . The first and second guide patterns  115 ,  130  and  130   a  may be formed of the same material. 
         [0037]    For instance, the first and second guide patterns  115 ,  130  and  130   a  may be formed of polysilicon and the mask layer  120  may be formed of an oxide layer. In some embodiments, the first and second guide patterns  115 ,  130  and  130   a  may be formed of an oxide layer and the mask layer  120  may be formed of polysilicon. 
         [0038]    Referring to  FIG. 1D , the mask layer  120  is planarized down to the top surface of the first guide patterns  115  to form preliminary mask patterns  120   a.  Each of the preliminary mask patterns  120   a  is formed between the adjacent first guide patterns  115 . Each of the preliminary mask pattern  120   a  includes the empty region  125 . Each of the preliminary mask pattern  120   a  includes a wall portion  121  disposed between the adjacent first guide patterns  115  and the second guide patterns  130  and  130   a,  and a base portion  122  disposed under the second guide patterns  130  and  130   a.  A top surface of the wall portion  121  in the illustrated embodiments is higher than that of the base portion  122 . The top surfaces of the first and second guide patterns  115 ,  130  and  130   a  are exposed by the formation of the preliminary mask patterns  120   a.    
         [0039]    Referring to  FIG. 1E , a photoresist pattern  135  is formed on an entire surface of the substrate  100 . The photoresist pattern  135  includes an opening  140 . The opening  140  exposes only the selected guide pattern  130   a  of the first and second guide patterns  115 ,  130  and  130   a.  A semiconductor pattern having a large line width will be formed under the selected guide pattern  130   a  by a subsequent process as described for illustrative purposes herein. As described above, the reference numeral  130   a  designates a selected one of the second guide patterns  130  and  130   a  for this purpose. In the illustrated embodiments, the selected guide pattern  130   a  may be one of the second guide patterns  130  and  130   a.  However, the selected guide pattern may be one of the first guide patterns  115 . In addition, in some embodiments, a plurality of selected guide patterns for larger width features may be provided on the substrate  100 . The number of the selected guide patterns may be two or more selected from the first guide patterns  115  and/or the second guide patterns  130  and  130   a.    
         [0040]    Referring to  FIG. 1F , the selected guide pattern  130   a  exposed by the opening  140  is removed to form a gap region  145 . The gap region  145  is a region where the selected guide pattern  130   a  is removed. Non-selected ones of the first and second guide patterns  115  and  130  remain after the selected guide pattern  130   a  is removed. The non-selected guide patterns  115  and  130  in some embodiments include at least one the first guide patterns  115  and one of the second guide patterns  130  adjacent to each other. Thus, after the gap region  145  is formed, both sidewalls of at least one of the wall portions  121  are surrounded by the first guide pattern  115  and the second guide pattern  130 . In the case that the selected guide pattern  130   a  is one of the second guide patterns  130  and  130   a,  the gap region  145  may correspond to the empty region  125 . When the selected guide pattern is one of the first guide patterns  115 , the gap region  145  is disposed between a pair of preliminary mask patterns  120   a  adjacent to each other. 
         [0041]    Subsequently, the photoresist pattern  135  is removed. A filling mask layer (pattern)  150  is formed on the substrate  100  to fill the gap region  145 . The filling mask layer  150  may be formed of a material having an etching selectivity with respect to the first and second guide patterns  115  and  130 . Also, the filling mask layer  150  may be formed of material having an etching selectivity with respect to the etching target layer  110 . The filling mask layer  150  may be formed of the same material as the mask layer  120 . 
         [0042]    Referring to  FIG. 1G , the filling mask layer  150  is planarized down to the top surfaces of the first and second guide patterns  115  and  130  to form a filling mask pattern  150   a  in the gap region  145 . The filling mask pattern  150   a  is in contact with a pair of the wall portions  121  that correspond to the both sidewalls of the gap region  145 . 
         [0043]    Referring to  FIG. 1H , the first and second guide patterns  115  and  130  are removed. The preliminary mask pattern  120   a  and the filling mask pattern  150   a  remain on the substrate  100 . Also, the base portion  122  disposed under the second guide patterns  130  is exposed. As shown in  FIG. 1H , the base portion covered with the filling mask pattern  150   a  is not exposed. That is, the base portions  122  disposed under the non-selected second guide patterns  130  are exposed. 
         [0044]    Subsequently, the exposed base portions  122  are anisotropically etched to expose the etching target layer  110  under the exposed base portion  122 . Mask patterns  120   b  and  155  are formed on the etching target layer  110  by removing the exposed base portions. When the exposed base portions  122  are etched, the wall portion  121  is also anisotropically etched. However, as the wall portion  121  is formed to be higher than the base portion  122 , the wall potions  121  remain on the etching target layer  110 . When the filling mask pattern  150   a  is formed of the same material as the preliminary mask layer  120   a,  the filling mask pattern  150   a  may also be anisotropically etched. In  FIG. 1H , the filling mask pattern  150   a  is formed of the same material as the mask layer  120 . 
         [0045]    The mask patterns  120   b  and  155  include first mask patterns  120   b  and a second mask pattern  155 . The second mask pattern  155  includes the anisotropically etched filling mask pattern and a pair of the anisotropically etched wall portions which are in contact with the both sides of the anisotropically etched filling mask pattern, respectively. The first mask patterns  120   b  correspond to the anisotropically etched wall portions being spaced apart from the second mask pattern  155 , respectively. Thus, a line width of the second mask pattern  155  is larger than that of the first mask pattern  120   b.    
         [0046]    Referring to  FIG. 1I , the etching target layer  110  is etched using the first and second mask patterns  120   b  and  155  as an etching mask to form first and second real semiconductor patterns  110   a  and  110   b.  The first real semiconductor pattern  110   a  is formed under the first mask pattern  120   b  and the second real semiconductor pattern  110   b  is formed under the second mask pattern  155 . The first and second mask patterns  120   b  and  155  are then removed. 
         [0047]    The first real semiconductor pattern  110   a  is defined by the first mask pattern  120   b.  The first mask pattern  120   b  includes the wall portion  121  of the preliminary mask pattern  120   a.  Thus, a line width of the first mask pattern  120   b  is determined by a width of the wall portion  121 . The width of the wall portion  121  is determined by a thickness of the mask layer  120 . Therefore, the line width of the first mask pattern  120   b  need not depend on the limits of the lithography process. That is, a distribution of the line width generated by the lithography process may not affect the line width consistency of the first mask patterns  120   b.  A uniformity of the line width of the first mask pattern  120   b  may, thus, be improved. Particularly, in the case of forming the mask layer  120  by means of an atomic layer deposition (ALD) process, the uniformity of the line width of the first mask pattern  120   b  may be significantly improved. 
         [0048]    Also, the second mask pattern  155  having a relatively large width as well as the first mask pattern  120   b  having a fine line width may be formed by the filling mask pattern  150   a.  As a result, the first real semiconductor patterns  110   a  having a fine line width and the second real semiconductor patterns  110   b  having a relatively large width may be formed simultaneously. 
         [0049]    The etching target layer  110  may be formed of conductive material. In this case, the first and second real semiconductor patterns  110   a  and  110   b  may be used as an interconnection line, such as a bit line or a word line, of a memory device (such as a direct random access memory (DRAM) device, a phase changeable memory device, and/or a flash memory device, etc). In this case, a single layered or a multi layered insulating layer may be disposed between the etching target layer  110  and the substrate  100 . 
         [0050]    In some embodiments, when the etching target layer  110  is formed of a hard mask, the first and second real semiconductor patterns  110   a  and  110   b  may be formed of hard mask patterns defining an active region. A method of forming a semiconductor device for such embodiments will be further described referring to  FIG. 1J . 
         [0051]    Referring to  FIG. 1J , the substrate  100  is etched using the first and second real semiconductor patterns  110   a  and  110   b  as an etching mask to form a trench  105  defining the active regions  103   a  and  103   b.  The trench  105  may extend in one direction. The trench  105  may have a groove shape. Also, the active regions  103   a  and  103   b  may extend in one direction, and the active regions  103   a  and  103   b  may have a line shape. The first active regions  103   a  having a small width are defined under the first real semiconductor pattern  110   a  and the second active region  103   b  having a relatively large width is defined under the second real semiconductor pattern  110   b.  A device isolation layer may be formed to fill the trench  105 . 
         [0052]    Further embodiments of the present invention will now be described. More particularly,  FIGS. 3A through 3G  are cross sectional views illustrating a method of forming a semiconductor device in accordance with further embodiments of the present invention,  FIG. 4  is a top plan view seen a direction B seen in  FIG. 3A , and  FIG. 5  is a top plan view seen from a direction C seen in  FIG. 3G . 
         [0053]    Referring to  FIGS. 3A and 4 , a device isolation layer is formed in a substrate  200  to define active regions  203  that are parallel with each other. The active regions  203  may be line shaped parallel regions as seen in plan view in  FIG. 4 . The active regions  203  may be formed using the same method as the first and second active regions  103   a  and  103   b  of the above described embodiments. In this case, an active region having a width larger than the active region  203  may also be formed in the substrate  200 . 
         [0054]    A tunnel insulating layer  205  and a charge storage layer  207  that are sequentially stacked are formed on the active region  203 . The tunnel insulating layer  205  may be formed of an oxide layer, such as a thermal oxide layer. The charge storage layer  207  may be formed of undoped polysilicon and/or doped polysilicon. In some embodiments, the charge storage layer  207  is formed on a limited portion of the active region  203 . 
         [0055]    In other embodiments, the charge storage layer  207  may be formed of an insulating material having a deep level trap. For example, the charge storage layer  207  may be formed of a silicon nitride layer and/or an insulating layer including a number of nanocrystals. The charge storage layer  207  may be formed on an entire surface of the substrate  200 . In some embodiments where the charge storage layer  207  is formed of insulating material having a trap of a deep level, the charge storage layer  207  may be formed only on a limited portion of the active region  203 . 
         [0056]    A blocking insulating layer  209  is formed on an entire surface of the substrate  200  including the charge storage layer  207 . The blocking insulating layer  209  may be formed of an oxide layer and/or an oxide-nitride-oxide (ONO) layer. When the blocking insulating layer  209  is formed of an oxide layer, the blocking insulating layer  209  may be formed to have a thickness greater than the tunnel insulating layer  205 . The blocking insulating layer  209  may include a high dielectric material having a high dielectric constant as compared with the tunnel insulating layer  205 . For instance, the blocking insulating layer  209  may include an insulating metal oxide, such as hafnium oxide and/or aluminum oxide. 
         [0057]    A control gate conductive layer  211  is formed on an entire surface of the substrate  200  including the blocking insulating layer  209 . The control gate conductive layer  211  may include a doped polysilicon, a metal (ex: tungsten or molybdenum, etc), a conductive metal nitride (ex: nitride titanium, nitride tantalum, or nitride tungsten, etc) and/or a metal silicide (ex: tungsten silicide or cobalt silicide, etc). 
         [0058]    A capping layer  213  may be formed on the control gate conductive layer  211 . The capping layer  213  may be formed of various materials, such as an oxide layer, a polysilicon layer or an oxide nitride layer, and/or the like. In another embodiment, the capping layer  213  may not be formed. 
         [0059]    First guide patterns  215   a,    215   b,  and  215   c  are formed on the capping layer  213  to be parallel to each other. The first guide patterns  215   a,    215   b,  and  215   c  may have a line shape and cross the active region  203 . The illustrated first guide patterns  215   a,    215   b,  and  215   c  include a string selection guide pattern  215   a,  a ground selection guide pattern  215   b,  and a plurality of cell guide patterns  215   c  disposed between the string and ground selection guide patterns  215   a  and  215   b.  The first guide patterns  215   a,    215   b,  and  215   c  may be formed to have substantially the same interval from each other. The interval between the first guide patterns  215   a,    215   b  and  215   c  may be larger than 1F (here, 1F means a minimum feature size). For instance, the interval between the first guide patterns  215   a,    215   b  and  215   c  may be 4F. 
         [0060]    In some embodiments, the cell guide patterns  215   c  have substantially the same line width with respect to each other. The string selection guide pattern  215   a  may have substantially the same line width as the ground selection guide pattern  215   b.  The string and ground selection guide patterns  215   a  and  215   b  may have the same line width as the cell guide pattern  215   c  or have a different line width from that of the cell guide pattern  215   c.    
         [0061]    Referring to  FIG. 3B , a mask layer  220  is conformally formed on an entire surface of the substrate  200  including the first guide patterns  215   a,    215   b  and  215   c.  The mask layer  220  may be formed of a material having an etching selectivity with respect to the first guide patterns  215   a,    215   b  and  215   c,  and the control gate conductive layer  211 . The mask layer  220  may be formed by a chemical vapor deposition (CVD) process and/or an atomic layer deposition (ALD) process. In some embodiments, the mask layer  220  is formed by an atomic layer deposition (ALD) process. 
         [0062]    Empty regions  225  are formed between the first guide patterns  215   a,    215   b  and  215   c  by conformally forming the mask layer  220 . The string selection guide pattern  215   a  includes a first side and a second side opposite to each other. The first cell guide patterns  215   c  are disposed at the first side of the string selection guide pattern  215   a.  The empty region  225  is also disposed at the second side of the string guide pattern  215   a.  The ground selection guide pattern  215   b  includes a first side and a second side opposite to each other. The cell guide patterns  215   c  are disposed at the first side of the ground selection guide pattern  215   b.  The empty region  225  is also disposed at the second side of the ground guide pattern  215   b.  The empty regions  225  formed at the second sides of the string and ground selection guide patterns  215   a  and  215   b  may have a width larger than the empty regions  225  formed between the first guide patterns  215   a,    215   b  and  215   c.    
         [0063]    Second guide patterns  230  are formed to fill the empty regions  225 , respectively. The second guide patterns  230  are formed of a material having an etching selectivity with respect to the mask layer  220 . The second guide patterns  230  may be formed of the same material as the first guide patterns  115 . For instance, the mask layer  220  may be formed of oxide and the first and second guide patterns  215   a,    215   b  and  215   c  may be formed of polysilicon. In some embodiments, the mask layer  220  may be formed of polysilicon and the first and second guide patterns  215   a,    215   b  and  215   c  may be formed of oxide. The method used in forming the second guide patterns  230  may be substantially the same method as described with reference to the second guide pattern  130  of  FIG. 1C . 
         [0064]    Referring to  FIG. 3C , the mask layer  220  is planarized down to the top surface of the first guide patterns  215   a,    215   b  and  215   c  to form preliminary mask patterns  220   a.  The preliminary mask pattern  220   a  includes a wall portion  221  disposed between first guide patterns  215   a,    215   b  and  215   c  and the second guide patterns  230  adjacent to each other, and includes a base portion  222  disposed under the second guide pattern  230 . A top surface of the wall portion  221  is higher than that of the base portion  222 . The preliminary mask patterns  220   a  are also formed on the second side of the string and ground selection guide patterns  215   a  and  215   b.    
         [0065]    A photoresist pattern  235  including first and second openings  240   a  and  240   b  is formed on an entire surface of the substrate  200 . The first opening  240   a  exposes the string selection guide pattern  215   a  and the second opening  240   b  exposes the ground selection guide pattern  215   b.    
         [0066]    Referring to  FIG. 3D , the exposed string and ground selection guide patterns  215   a  and  215   b  are removed to form first and second gap regions  245   a  and  245   b,  respectively. The first gap region  245   a  is a region where the string selection guide pattern  215   a  is removed and the second gap region  245   b  is a region where the ground selection guide pattern  215   b  is removed. 
         [0067]    The photoresist pattern  235  is removed and a filling mask layer  250  is formed on an entire surface of the substrate  200  to fill the first and second gap regions  245   a  and  245   b.  The filling mask layer  250  is formed of material having an etching selectivity with respect to the cell guide patterns  215   c,  the second guide patterns  230  and the control gate conductive layer  211 . The filling mask layer  250  may be formed of the same material as the mask layer  220 . 
         [0068]    Referring to  FIG. 3E , the filling mask layer  250  is planarized down to the top surfaces of the cell guide patterns  230  and the second guide pattern  230  to form first and second filling mask patterns  250   a  and  250   b  filling the first and second gap regions  245   a  and  245   b,  respectively. 
         [0069]    The cell guide patterns  215   c  and the second guide patterns  230  are removed. As a result, the base portions  222  disposed under the second guide patterns  230  are exposed. The first and second filling mask patterns  250   a  and  250   b  and the preliminary mask patterns  220   a  remain. 
         [0070]    Referring to  FIG. 3F , the exposed base portions  222  are anisotropically etched to form mask patterns  220   c,    255   a  and  255   b.  As the base portion  222  and the wall portion  221  are a portion of the mask layer  220 , the top portion of the wall portion  221  may also be etched during the etching of the base portion  222 . The mask patterns  220   c,    255   a  and  255   b  include cell mask patterns  220   c,  a string selection mask pattern  255   a  and a ground selection mask pattern  255   b.  The mask patterns include an anisotropically etched wall portion. The string selection mask pattern  255   a  includes the anisotropically etched first filling mask pattern  250   a  and the pair of anisotropically etched wall portion which is in contact with the both sides of the anisotropically etched first filling mask pattern  250   a.  The ground selection mask pattern  255   b  includes the anisotropically etched second filling mask pattern  250   b  and the pair of anisotropically etched wall portion which is in contact with the both sides of the anisotropically etched second filling mask pattern  250   b.  Due to the first and second filling mask patterns  250   a  and  250   b,  the string and ground selection mask patterns  255   a  and  255   b  have a width larger than the cell mask patterns  220   c.    
         [0071]    The cell mask patterns  220   c  include the wall portions  221  that remain between the string and ground selection mask patterns  255   a  and  255   b,  respectively. The wall portions  221  included in the cell mask patterns are shown spaced apart from the string and ground selection mask patterns  255   a  and  255   b.  A line width of the cell mask pattern  220   c  is determined by a line width of the wall portion  221 . The line width of the wall portion  221  is determined by a thickness of the mask layer  220 . Thus, a distribution of the line width generated by a lithography process is not limiting for the cell mask patterns  220   c.  The line widths of the cell mask patterns  220   c  can be provided an excellent uniformity in some embodiments as a result. When the cell mask layer  220  is formed by an atomic layer deposition (ALD) process, the uniformity of the line width of the cell mask patterns  220   c  may be greatly improved. Also, the string and ground selection mask patterns  255   a  and  255   b  may be formed to have a larger width by the first and second filling mask patterns  250   a  and  250   b.    
         [0072]    Referring to  FIGS. 3G and 5 , when the charge storage layer  207  is formed of polysilicon, the capping layer  213 , control gate conductive layer  211 , blocking insulating layer  209  and charge storage layer  207  may be sequentially etched, using the string selection, cell and ground selection mask patterns  255   a,    220   c  and  255   b  as an etching mask, to form a string selection line (SSL), word lines (WL) and a ground selection line (GSL). The string selection line (SSL), word lines (WL) and the ground selection line (GSL) are formed under the string selection mask pattern  255   a,  the cell mask pattern  220   c  and the ground selection mask pattern  255   b,  respectively. When forming the control gate conductive layer  211 , holes may be formed to penetrate the blocking insulating layer  209  where the string and ground selection lines (SSL) and (GSL) are formed. Thus, a specific portion of the control gate conductive layer  211  and the charge storage layer  207  under the string selection line (SSL) may be connected to each other through the holes. Also, the specific portion of the control gate conductive layer  211  and the charge storage layer  207  under the ground selection line (GSL) may be connected to each other through the holes. 
         [0073]    In further embodiments, when the charge storage layer  207  is formed of insulating material including deep level traps, the capping layer  213  and the control gate conductive layer  211  may be sequentially etched, using the string selection, cell and ground selection mask patterns  255   a,    220   c  and  255   b  as an etching mask, to form the string selection line (SSL), the word lines (WL) and the ground selection line (GSL). The blocking insulating layer  209  may be used as an etching stop layer during the etching process. Charges stored in the deep level traps may not move to other cells. Accordingly, memory cell interference may be limited or even prevented. As a result, the charge storage layer  207  may not be divided. In some embodiments, when the charge storage layer  207  is formed of an insulating material including deep level traps, the capping layer  213 , the control gate conductive layer  211 , the blocking insulating layer  209  and the charge storage layer  207  may be successively etched using the mask patterns  255   a,    220   c  and  255   b  as an etching mask. At this time, the tunnel insulating layer  205  may be used as an etching stop layer during the etching process. 
         [0074]    The mask patterns  255   a,    220   c  and  255   b  may be removed after the string selection line (SSL), the word lines (WL) and the ground selection line (GSL) are formed. 
         [0075]    Using the string selection line (SSL), the word lines (WL) and the ground selection line (GSL) as a mask, a dopant ion implantation process may be performed in the active region  203  to form a common drain region  260   d,  cell source/drain regions  260   c  and a common source region  260   s.  The common drain region  260   d  is formed in the active region  203  of one side of the string selection line (SSL). The common source region  260   s  is formed in the active region  203  of one side of the string selection line (GSL). The cell source/drain regions  260   c  are formed in the active region  203  on both sides of the word line (WL). The common drain region  260   d  may be formed under the second guide pattern  230 , which is disposed at the second side of the string selection guide pattern  215   a.  The common source region  260   s  may be formed under the second guide pattern  230 , which is disposed at the second side of the ground selection guide pattern  215   b.    
         [0076]    A word line (WL) most adjacent to the string selection line (SSL) and a word line (WL) most adjacent to the ground selection line (GSL) may be used as a dummy line. Thus, a first space between the string selection line (SSL) and an actually operating word line (WL) most adjacent to the string selection line (SSL) and a second space between the ground selection line (GSL) and an actually operating word line (WL) most adjacent to the ground selection line (GSL) may increase. The first and second spaces may be formed to have the same dimension and a characteristic of a NAND-type nonvolatile memory device may be improved by increasing the first and second spaces. 
         [0077]    According to methods of forming the semiconductor device described above, the line width of the cell mask pattern  220   c  defining the word line (WL) is determined by the thickness of the mask layer  220 . Thus, the problems resulting from reliance on a conventional lithography process may be limited or even prevented. Also, using the filling mask patterns  250   a  and  250   b,  the string and ground selection mask patterns  255   a  and  255   b  having a relatively large width may be formed. 
         [0078]    In addition, the number of the wall portions  221  disposed between the string and ground selection guide patterns  215   a  and  215   b  may be an even number. Accordingly, the number of the cell mask patterns  220   c  disposed between the string and ground selection mask patterns  255   a  and  255   b  may be even number. An even number of word lines may be required for the cell string of the flash memory device. Thus, additional processes may not be required for forming the even number of word lines. As a result, the manufacturing process may be simplified. 
         [0079]    The foregoing is illustrative of the present invention and is not to be construed as limiting thereof. Although a few embodiments of the present invention have been described, those skilled in the art will readily appreciate that many modifications are possible in the embodiments without materially departing from the novel teachings and advantages of the present invention. Accordingly, all such modifications are intended to be included within the scope of the present invention as defined in the claims. Therefore, it is to be understood that the foregoing is illustrative of the present invention and is not to be construed as limited to the specific embodiments disclosed, and that modifications to the disclosed embodiments, as well as other embodiments, are intended to be included within the scope of the appended claims. The present invention is defined by the following claims, with equivalents of the claims to be included therein.