Patent Publication Number: US-2023137846-A1

Title: Semiconductor device and methods of manufacturing the same

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is based on and claims priority under 35 U.S.C. § 119 to Korean Patent Application No. 10-2021-0146063, filed on Oct. 28, 2021, in the Korean Intellectual Property Office, the disclosure of which is incorporated by reference herein in its entirety. 
     BACKGROUND 
     Inventive concepts relate to a semiconductor device and/or a method of manufacturing the same, and more particularly, to a semiconductor device including a cell capacitor and/or a method of manufacturing the same. 
     As semiconductor devices are being downscaled, sizes of individual micro circuit patterns for implementing semiconductor devices are being further reduced. Also, as the size of individual microcircuit patterns is reduced, the difficulty of a manufacturing process may increase due to a difference in pattern density between the interior of a cell array area and a peripheral area. 
     SUMMARY 
     Inventive concepts provide a semiconductor device capable of preventing or reducing the likelihood of and/or impact from process defects due to a step difference occurring at edge portions of a cell array area. 
     Alternatively or additionally, inventive concepts provide a method of manufacturing a semiconductor device capable of preventing or reducing the likelihood of and/or impact from process defects due to a step difference occurring at edge portions of a cell array area. 
     According to some example embodiments, there is provided a semiconductor device including a substrate including a cell array area and a peripheral circuit area. The semiconductor device includes a plurality of first active areas defined in the cell array area and at least one second active area defined in the peripheral circuit area; a plurality of bit lines in the cell array area of the substrate and extending in a first direction; a plurality of cell pad structures between the bit lines and each including a first conductive layer, a first intermediate layer, and a first metal layer that are sequentially arranged on a top surface of the first active area; and a peripheral circuit gate electrode on the peripheral circuit area of the substrate and including a second conductive layer, a second intermediate layer, and a second metal layer sequentially arranged on the at least one second active area. 
     According to some example embodiments, there is provided a semiconductor device including a substrate including a cell array area, a boundary area, and a peripheral circuit area and including a plurality of first active areas defined in the cell array area and at least one second active area defined in the peripheral circuit area; a plurality of bit lines in the cell array area of the substrate and extending in a first direction; a plurality of cell pad structures between two adjacent bit lines from among the plurality of bit lines and each including a first conductive layer and a first metal layer that are sequentially arranged on a top surface of the first active area; and a peripheral circuit gate electrode on the peripheral circuit area of the substrate and including a second conductive layer and a second metal layer sequentially arranged on the at least one second active area. A height of the cell pad structures is substantially the same as a height of the peripheral circuit gate electrode. 
     According to some example embodiments, there is provided a semiconductor device including a substrate including a cell array area, a boundary area, and a peripheral circuit area and including a plurality of first active areas defined in the cell array area and at least one second active area defined in the peripheral circuit area; a plurality of bit lines arranged in the cell array area of the substrate and extending in a first direction; a bit line contact between the bit lines and the first active areas and electrically connecting the bit lines to the first active areas; a bit line contact spacer surrounding sidewalls of the bit line contact; a plurality of cell pad structures between two adjacent bit lines from among the plurality of bit lines and each including a first conductive layer, a first intermediate layer, and a first metal layer that are sequentially arranged on a top surface of the first active area; a plurality of landing pads respectively arranged on the cell pad structures; and a peripheral circuit gate electrode on the peripheral circuit area of the substrate and including a second conductive layer, a second intermediate layer, and a second metal layer sequentially arranged on the at least one second active area. The second metal layer includes the same material as the material included in the first metal layer. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Embodiments of inventive concepts will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings in which: 
         FIG.  1    is a layout diagram showing a semiconductor device according to some example embodiments; 
         FIG.  2    is an enlarged layout view of a portion A of  FIG.  1   : 
         FIG.  3    is a cross-sectional view taken along a line B 1 -B 1 ′ of  FIG.  2   ; 
         FIG.  4    is a cross-sectional view taken along a line B 2 -B 2 ′ of  FIG.  2   ; 
         FIG.  5    is an enlarged cross-sectional view of a portion CX 1  of  FIG.  3   ; 
         FIG.  6    is an enlarged cross-sectional view of a portion CX 2  of  FIG.  3   ; 
         FIG.  7    is a cross-sectional view of a semiconductor device according to some example embodiments of inventive concepts; 
         FIG.  8    is an enlarged cross-sectional view of a portion CX 1  of  FIG.  7   ; 
         FIG.  9    is an enlarged cross-sectional view of a portion CX 2  of  FIG.  7   ; 
         FIGS.  10 A to  21    are cross-sectional views showing a method of manufacturing a semiconductor device according to some example embodiments, wherein, in detail,  FIGS.  10 A .  12  to  18 ,  19 A,  20 , and  21  are cross-sectional views corresponding to cross-sections taken along a line B 1 -B 1 ′ of  FIG.  2   , and  FIGS.  10 B,  11 , and  19 B  are cross-sectional views corresponding to cross-sections taken along a line B 2 -B 2 ′ of  FIG.  2   . 
     
    
    
     DETAILED DESCRIPTION OF VARIOUS EXAMPLE EMBODIMENTS 
       FIG.  1    is a layout diagram showing a semiconductor device  100  according to some example embodiments.  FIG.  2    is an enlarged layout view of a portion A of  FIG.  1   .  FIG.  3    is a cross-sectional view taken along a line B 1 -B 1 ′ of  FIG.  2   .  FIG.  4    is a cross-sectional view taken along a line B 2 -B 2 ′ of  FIG.  2   .  FIG.  5    is an enlarged cross-sectional view of a portion CX 1  of  FIG.  3   .  FIG.  6    is an enlarged cross-sectional view of a portion CX 2  of  FIG.  3   . 
     Referring to  FIGS.  1  to  6   , the semiconductor device  100  may include a substrate  110  including a cell array area MCA and a peripheral circuit area PCA. The cell array area MCA may be or may include a memory cell area of a DRAM device, and the peripheral circuit area PCA may be or may include a core area or a peripheral circuit area of the DRAM device; however, example embodiments are not limited thereto. For example, the cell array area MCA may include a cell transistor CTR and a capacitor structure  180  connected thereto, and the peripheral circuit area PCA may include a peripheral circuit transistor PTR for transferring signals and/or power to the cell transistor CTR included in the cell array area MCA. In some example embodiments, the peripheral circuit transistor PTR may configure various circuits such as a command decoder, control logic, an address buffer, a row decoder, a column decoder, a sense amplifier, a redundancy circuit, and/or a data input/output circuit. 
     A device isolation trench  112 T may be formed in the substrate  110 , and a device isolation layer  112  may be formed in the device isolation trench  112 T. The device isolation layer  112  may define a plurality of first active areas AC 1  on the substrate  110  in the cell array area MCA and may define a plurality of second active areas AC 2  on the substrate  110  in the peripheral circuit area PCA. 
     A boundary trench  114 T may be formed in a boundary area BA between the cell array area MCA and the peripheral circuit area PCA, and a boundary structure  114  may be formed in the boundary trench  114 T. When viewed from above (e.g. in plan view), the boundary trench  114 T may be provided to surround all sides. e.g. four sides of the cell array area MCA. The boundary structure  114  may include a buried insulation layer  114 A, an insulation liner  114 B. and a gap-fill insulation layer  114 C arranged inside the boundary trench  114 T. 
     The buried insulation layer  114 A may be conformally disposed on the inner wall of the boundary trench  114 T. In some example embodiments, the buried insulation layer  114 A may include silicon oxide. For example, the buried insulation layer  114 A may include silicon oxide formed through one or more of an atomic layer deposition (ALD) process, a chemical vapor deposition (CVD) process, a plasma enhanced CVD (PECVD) process, a low pressure CVD (LPCVD) process, etc. 
     The insulation liner  114 B may be conformally disposed on the inner wall of the boundary trench  114 T on the buried insulation layer  114 A. In some example embodiments, the insulation liner  114 B may include silicon nitride. For example, the insulation liner  114 B may include silicon nitride formed through one or more of an ALD process, a CVD process, a PECVD process, an LPCVD process, etc. 
     The gap-fill insulation layer  114 C may fill the boundary trench  114 T on the insulation liner  114 B. In some example embodiments, the gap-fill insulation layer  114 C may include one or more of a silicon oxide like Tonen Silazene (TOSZ), undoped silicate glass (USG), boro-phospho-silicate glass (BPSG), phosphosilicate glass (PSG), flowable oxide (FOX), plasma enhanced deposition of tetra-ethyl-ortho-silicate (PE-TEOS), or fluoride silicate glass (FSG). 
     In the cell array area MCA, the first active areas AC 1  may be arranged to have long axes in a diagonal direction with respect to a first horizontal direction X and a second horizontal direction Y. The diagonal direction may be a direction of between 10 degrees and 80 degrees with respect to the first horizontal direction X and the second horizontal direction Y, for example may be a direction 70 degrees with respect to the first horizontal direction X; however, example embodiments are not limited thereto. A plurality of word lines WL may extend parallel to one another along the first horizontal direction X across the first active areas AC 1 . A plurality of bit lines BL may extend parallel to one another along the second horizontal direction Y on the word lines WL. The bit lines BL may be connected to the first active areas AC 1  via direct contacts DC. 
     A plurality of cell pad structures  130  may be formed between two bit lines BL adjacent to each other from among the bit lines BL. The cell pad structures  130  may be arranged in a row in the first horizontal direction X and the second horizontal direction Y. A plurality of landing pads LP may be formed on the cell pad structures  130 . The cell pad structures  130  and the landing pads LP may connect lower electrodes  182  of the capacitor structure  180  formed over the bit lines BL to the first active areas AC 1 . The landing pads LP may be arranged to partially overlap the cell pad structures  130 , respectively. 
     The substrate  110  may include silicon. e.g., monocrystalline silicon, polycrystalline silicon, or amorphous silicon. In some example embodiments, the substrate  110  may include at least one selected from among Ge, SiGe, SiC, GaAs, InAs, and InP. In some example embodiments, the substrate  110  may include a conductive region, e.g., a well doped with an impurity or a structure doped with an impurity. The device isolation layer  112  may include an oxide film, a nitride film, or a combination thereof. 
     In the cell array area MCA, a plurality of word line trenches  120 T extending in a first direction (X direction) may be arranged on the substrate  110 , and a buried gate structure  120  may be disposed in the word line trenches  120 T. The buried gate structure  120  may include gate dielectric layers  122 , gate electrodes  124 , and capping insulation layers  126  respectively arranged in the word line trenches  120 T. A plurality of gate electrodes  124  may correspond to the word lines WL shown in  FIG.  1   . 
     A plurality of gate dielectric layers  122  may include one or more of a silicon oxide film, a silicon nitride film, a silicon oxynitride film, an oxide/nitride/oxide (ONO) film, or a high-k dielectric film having a dielectric constant higher than that of the silicon oxide film. The gate electrodes  124  may include Ti, TiN, Ta, TaN, W, WN, TiSiN, WSiN, or a combination thereof. A plurality of capping insulation layers  126  may include a silicon oxide film, a silicon nitride film, a silicon oxynitride film, or a combination thereof. 
     The word line trenches  120 T may extend from the cell array area MCA into the boundary area BA, and respective end portions of the word line trenches  120 T may vertically overlap the boundary structure  114  in the boundary area BA. 
     A buffer layer  118  may be formed on the substrate  110 , the buried gate structure  120 , and the boundary structure  114  in the boundary area BA. The buffer layer  118  may include an oxide film, a nitride film, or a combination thereof. 
     A plurality of bit line contacts or direct contacts DC may be formed in a plurality of bit line contact holes or direct contact holes DCH on the substrate  110 . The direct contacts DC may be connected to the first active area AC 1 . The direct contacts DC may include TiN, TiSiN. W, tungsten silicide, doped polysilicon, or a combination thereof. 
     A bit line contact spacer or direct contact spacer DCS may be disposed on the inner wall of the direct contact hole DCH. The direct contact spacer DCS may be disposed on the lower sidewall of the direct contact hole DCH and may cover the lower portion of the direct contact DC. 
     The bit lines BL may extend long in the second horizontal direction Y over the substrate  110  and the plurality of direct contacts DC. The bit lines BL may be connected to the first active areas AC 1  via the direct contacts DC, respectively. The bit lines BL may include ruthenium (Ru), tungsten (W), cobalt (Co), titanium (Ti), titanium nitride (TiN), or a combination thereof. 
     The bit lines BL may be covered by a plurality of insulation capping structures  140 , respectively. The insulation capping structures  140  may extend in the second horizontal direction Y on the bit lines BL. The insulation capping structures  140  may each include a lower capping pattern  142 A and an upper capping pattern  144 A. 
     Bit line spacers  150 A may be arranged on both sidewalls of each of the bit lines BL. The bit line spacers  150 A may extend in the second horizontal direction Y on both sidewalls of the bit lines BL, and portions of the bit line spacers  150 A may extend into the direct contact holes DCN and cover the upper portion of the sidewall of the direct contacts DC. Although  FIG.  3    shows that the bit line spacer  150 A is a single material layer, in some example embodiments, the bit line spacer  150 A may be formed as a stacked structure of a plurality of spacer layers (not shown), and at least one of the spacer layers may be an air spacer. 
     The cell pad structures  130  may be arranged between the bit lines BL. For example, one cell pad structure  130  may be disposed between two adjacent bit lines BL at a vertical level lower than that of the bit lines BL. For example, insulation patterns  152  may be disposed between the two cell pad structures  130  arranged in the first horizontal direction X and between two cell pad structures  130  arranged in the second horizontal direction Y, and the insulation pattern  152  may electrically separate two adjacent cell pad structures  130  from each other. Also, a lower portion of the sidewall of the cell pad structure  130  may contact the direct contact spacer DCS, and an upper portion of the sidewall of the cell pad structure  130  may contact the bit line spacer  150 A. 
     In some example embodiments, the cell pad structures  130  may include a first conductive layer  132 A, a first intermediate layer  134 A, and a first metal layer  136 A sequentially arranged on the first active area AC 1 . In some example embodiments, the first conductive layer  132 A may include Si, Ge, W, WN, CO, Ni, Al, Mo, Ru, Ti, TiN, Ta, TaN, Cu, or a combination thereof. The first intermediate layer  134 A and the first metal layer  136 A may each include TiN, TiSiN, W, tungsten silicide, or a combination thereof. 
     As shown in  FIG.  5   , the bottom surface of the first conductive layer  132 A may be disposed at a level lower than that of a top surface AC 1 _T of the first active area AC 1 , and the first conductive layer  132 A may be disposed to cover the top surface AC 1 _T and a sidewall AC 1 _S of the first active area AC 1 . Therefore, a relatively large contact area may be secured between the first conductive layer  132 A and the first active area AC 1 . In some example embodiments, unlike as shown in  FIG.  5   , the bottom surface of the first conductive layer  132 A may be disposed at substantially the same level as the top surface AC 1 _T of the first active area AC 1 , and thus the bottom surface of the first conductive layer  132 A may have a flat profile. 
     An insulation layer  154  may be disposed on the cell pad structure  130  to cover the cell pad structure  130  and the insulation pattern  152 . 
     A plurality of insulation fences  156  may be arranged in the second horizontal direction Y between two adjacent bit lines BL. The insulation fences  156  may be arranged on the insulation layer  154  at positions to vertically overlap the word line trenches  120 T. 
     The landing pads LP may be arranged on the cell pad structures  130 . The landing pads LP may each include a conductive barrier film  162 A and a landing pad conductive layer  164 A. The conductive barrier film  162 A may include Ti, TiN, or a combination thereof. The landing pad conductive layer  164 A may include a metal, a metal nitride, a conductive polysilicon, or a combination thereof. For example, the landing pad conductive layer  164 A may include W. The landing pads LP may have a pattern shape of a plurality of islands when viewed from above. 
     The landing pads LP may be electrically insulated from one another by an insulation pattern  166  surrounding the landing pads LP. The insulation pattern  166  may include at least one of silicon nitride, silicon oxide, and silicon oxynitride. 
     A first etch stop layer  172  may be disposed on the landing pads LP and the insulation pattern  166  in the cell array area MCA. The capacitor structure  180  may be disposed on the first etch stop layer  172 . The capacitor structure  180  may include a plurality of lower electrodes  182 , a capacitor dielectric layer  184 , and an upper electrode  186 . 
     The lower electrodes  182  may penetrate through the first etch stop layer  172  and extend in a vertical direction Z on the landing pads LP. The bottom portions of the lower electrodes  182  may penetrate through the first etch stop layer  172  and connected to the landing pads LP. The capacitor dielectric layer  184  may be disposed on the lower electrodes  182 . The upper electrode  186  may be disposed on the capacitor dielectric layer  184  to cover the lower electrodes  182 . 
     In some example embodiments, the capacitor dielectric layer  184  may include at least one of zirconium oxide, hafnium oxide, titanium oxide, niobium oxide, tantalum oxide, yttrium oxide, strontium titanium oxide, barium strontium titanium oxide, scandium oxide, and lanthanide oxide. The lower electrodes  182  and the upper electrode  186  may include at least one selected from among metals such as ruthenium (Ru), titanium (Ti), tantalum (Ta), niobium (Nb), iridium (Ir), molybdenum (Mo), and tungsten (W), conductive metal nitrides such as titanium nitride (TiN), tantalum nitride (TaN), niobium nitride (NbN), molybdenum nitride (MoN), and tungsten nitride (WN), and conductive metal oxides such as iridium oxide (IrO 2 ), ruthenium oxide (RuO 2 ), and strontium ruthenium oxide (SrRuO 3 ). 
     In some example embodiments, the lower electrodes  182  may each have a pillar shape extending in the vertical direction Z, and the lower electrodes  182  may each have a circular horizontal cross-section. However, the horizontal cross-sectional shape of the lower electrodes  182  is not limited thereto, and the lower electrodes  182  may have a horizontal cross-section of various polygonal shapes and rounded polygonal shapes such as an ellipse, a square, a rounded square, a rhombus, a trapezoid, etc. Alternatively or additionally, although  FIG.  3    shows that the lower electrodes  182  have a pillar shape having circular horizontal cross-sections throughout the entire heights thereof, in some example embodiments, the lower electrodes  182  may have a cylindrical shape with a closed bottom. 
     The peripheral circuit transistor PTR may be disposed on the second active area AC 2  in the peripheral circuit area PCA. The peripheral circuit transistor PTR may include a gate dielectric layer  116 , a peripheral circuit gate electrode PGS, and a gate capping pattern  142 B that are sequentially stacked on the second active area AC 2 . 
     The gate dielectric layer  116  may include at least one selected from among a silicon oxide film, a silicon nitride film, a silicon oxynitride film, an oxide/nitride/oxide (ONO) film, or a high-k dielectric film having a dielectric constant higher than that of the silicon oxide film. The gate capping pattern  142 B may include a silicon nitride film. 
     The peripheral circuit gate electrode PGS may include a second conductive layer  132 B, a second intermediate layer  134 B, and a second metal layer  136 B. In some example embodiments, the second conductive layer  132 B may include Si, Ge, W, WN, Co, Ni, Al, Mo, Ru, Ti, TiN, Ta, TaN, Cu, or a combination thereof. The second intermediate layer  134 B and the second metal layer  136 B may each include TiN, TiSiN, W, tungsten silicide, or a combination thereof. 
     In some example embodiments, the materials constituting or included in the second conductive layer  132 B, the second intermediate layer  134 B, and the second metal layer  136 B may be identical to the materials constituting or included in the first conductive layer  132 A, the first intermediate layer  134 A, and the first metal layer  136 A included in the cell pad structure  130  in the cell array area MCA, respectively. For example, the peripheral circuit gate electrode PGS may be simultaneously formed during a process of forming the cell pad structure  130 . In some example embodiments, because the cell pad structure  130  is formed at the same time as the peripheral circuit gate electrode PGS, the materials included in the second conductive layer  132 B, the second intermediate layer  134 B, and the second metal layer  136 B may be exactly the same as the respective materials included in the first conductive layer  132 A, the first intermediate layer  134 A, and the first metal layer  136 A included in the cell pad structure  130  in the cell array area MCA. In some example embodiments, the peripheral circuit gate electrode PGS is not formed at the same time as that of the bit line BL. Products and/or devices formed with such a process may have a different structure than products and/or devices formed with a typical process, insofar as the materials may be the same and/or the thickness may be the same. 
     As shown in  FIGS.  5  and  6   , the first metal layer  136 A included in the cell pad structure  130  may have a first height h 11  in the vertical direction Z, and the second metal layer  136 B included in the peripheral circuit gate electrode PGS may have a second height h 12  in the vertical direction Z. In some example embodiments, the second height h 12  may be substantially the same as the first height h 11 . For example, the first metal layer  136 A and the second metal layer  136 B may be formed during the same process by using the same material, and thus the first height h 11  of the first metal layer  136 A may be equal to the second height h 12  of the second metal layer  136 B. 
     Alternatively or additionally, the bit line BL may have a third height h 13  in the vertical direction Z, and the third height h 13  may be different from the first height h 11  and the second height h 12 . Alternatively or additionally, the material constituting the bit line BL may be different from the material constituting the second metal layer  136 B. In some embodiments, the second metal layer  136 B included in the peripheral circuit gate electrode PGS may include tungsten (W), the first metal layer  136 A included in the cell pad structure  130  may include tungsten (W), and the bit line BL may include ruthenium (Ru). However, inventive concepts are not limited thereto. 
     The peripheral circuit gate electrode PGS and both sidewalls of the gate capping pattern  142 B may be covered by insulation spacers  150 B. The insulation spacers  150 B may include an oxide layer, a nitride layer, or a combination thereof. The peripheral circuit transistor PTR and the insulation spacers  150 B may be covered by a passivation layer  146 , and a first interlayer insulation layer  148  may be disposed on the passivation layer  146  to fill the space between two adjacent peripheral circuit transistors PTR. A capping insulation layer  144 B may be disposed on the first interlayer insulation layer  148  and the passivation layer  146 . 
     A contact plug CP may be formed in a contact hole CPH vertically penetrating through the first interlayer insulation layer  148  and the capping insulation layer  1448  in the peripheral circuit area PCA. The contact plug CP may include a conductive barrier film  162 B and a landing pad conductive layer  164 B, similar to the landing pads LP formed in the cell array area MCA. A metal silicide layer (not shown) may be provided between the second active area AC 2  and the contact plug CP. 
     A second etch stop layer  174  covering the contact plug CP may be disposed on the capping insulation layer  144 B. A second interlayer insulation layer  190  covering the capacitor structure  180  may be disposed on the second etch stop layer  174 . 
     As shown in  FIG.  3   , the outermost cell pad structure  130  from among the cell pad structures  130  may extend onto the boundary area BA. The cell pad structure  130  disposed on the boundary area BA may be referred to as a cell pad extension  130 _E. The cell pad extension  130 _E may include a first portion  130 P 1  and a second portion  130 P 2 . The first portion  130 P 1  may be disposed on the first active area AC 1  and the device isolation layer  112 , and the second portion  130 P 2  may be disposed on the buffer layer  118 . Due to the thickness of the buffer layer  118 , the second portion  130 P 2  may have the top surface disposed at a higher level than the top surface of the first portion  130 P 1 . 
     An edge conductive layer BL_E may be disposed on the second portion  130 P 2  of the cell pad extension  130 _E. The edge conductive layer BL_E may refer to or correspond to a portion of a bit line conductive layer  138  (refer to  FIG.  16   ), which is for forming the bit line BL and remains after a process of patterning the bit line BL. However, in some example embodiments, a process for removing the edge conductive layer BL_E may be further performed. In this case, the edge conductive layer BL_E may be omitted. 
     In general or typically, the peripheral circuit gate electrode PGS is formed to have the same stack configuration as that of the bit line BL. For example, the peripheral circuit gate electrode PGS is formed, such that the bit line BL and a metal layer included in the peripheral circuit gate electrode PGS include the same material and/or have the same height. However, in a process for patterning the bit line BL, it becomes difficult to precisely control the patterning process due to a step or a level difference of the top surface of the cell pad extension  130 _E disposed in the boundary area BA, and thus a process defect may occur. 
     However, according to some example embodiments, the cell pad structure  130  and the peripheral circuit gate electrode PGS may be formed to have the same stack configuration. Therefore, a process defect due to a step or a level difference of the top surface of the cell pad extension  130 _E disposed in the boundary area BA may be prevented or reduced in likelihood of and/or impact from occurring. Alternatively or additionally, since a material included in the bit line BL may be selected independently from a material constituting the peripheral circuit gate electrode PGS, performance improvement or optimization of the semiconductor device  100  may be implemented. 
       FIG.  7    is a cross-sectional view of a semiconductor device  10 A according to some example embodiments.  FIG.  8    is an enlarged cross-sectional view of a portion CX 1  of  FIG.  7   .  FIG.  9    is an enlarged cross-sectional view of a portion CX 2  of  FIG.  7   . In  FIGS.  7  to  9   , reference numerals same as those in  FIGS.  1  to  6    denote the same elements. 
     Referring to  FIGS.  7  to  9   , a peripheral circuit gate electrode PGSA may include the second conductive layer  132 B, the second intermediate layer  134 B, the second metal layer  136 B, and a third metal layer  138 B that are sequentially stacked on the gate dielectric layer  116 . The third metal layer  138 B may include ruthenium (Ru), tungsten (W), cobalt (Co), titanium (Ti), titanium nitride (TiN), or a combination thereof. 
     In some example embodiments, the third metal layer  138 B may include the same material as that of the bit line BL. For example, the third metal layer  138 B and the bit line BL may be formed during the same process by using the same material, and thus a fourth height h 14  of the third metal layer  138 B may be substantially the same as the third height h 13  of the bit line BL. 
     In some example embodiments, the second conductive layer  132 B, the second intermediate layer  134 B, and the second metal layer  136 B of the peripheral circuit gate electrode PGSA is formed by using the same material as the first cell pad structure  130 , and the third metal layer  138 B of the peripheral circuit gate electrode PGSA is formed by using the same material as the bit line BL. Therefore, a process defect due to a step or a level difference of the top surface of the cell pad extension  130 _E disposed in the boundary area BA may be prevented or reduced in likelihood of and/or impact from occurrence. Alternatively or additionally, since a material constituting the peripheral circuit gate electrode PGSA may be selected independently from a material included in the bit line BL, performance improvement or optimization of the semiconductor device  100 A may be implemented. 
       FIGS.  10 A to  21    are cross-sectional views showing a method of manufacturing the semiconductor device  100  according to some example embodiments. In detail,  FIGS.  10 A,  12  to  18 ,  19 A,  20 , and  21    are cross-sectional views corresponding to cross-sections taken along a line B 1 -B 1 ′ of  FIG.  2   , and  FIGS.  10 B,  11 , and  19 B  are cross-sectional views corresponding to cross-sections taken along a line B 2 -B 2 ′ of  FIG.  2   . In  FIGS.  10 A to  21   , reference numerals same as those in  FIGS.  1  to  9    denote the same elements. 
     Referring to  FIGS.  10 A and  10 B , a plurality of device isolation trenches  112 T may be formed in the cell array area MCA and the peripheral circuit area PCA of the substrate  110 , and the boundary trench  114 T may be formed in the boundary area BA of the substrate  110 . 
     Thereafter, the device isolation layer  112  filling the device isolation trenches  112 T may be formed in the cell array area MCA and the peripheral circuit area PCA. As the device isolation layer  112  is formed, the first active areas AC 1  are defined in the cell array area MCA of the substrate  110 , and the second active area AC 2  is defined in the peripheral circuit area PCA. 
     In some example embodiments, the device isolation layer  112  may be formed by using silicon oxide, silicon nitride, silicon oxynitride, or a combination thereof. In some example embodiments, the device isolation layer  112  may be formed as a double-layer structure including a silicon oxide layer and a silicon nitride layer, but inventive concepts are not limited thereto. 
     Thereafter, the buried insulation layer  114 A, the insulation liner  114 B, and the gap-fill insulation layer  114 C are sequentially formed on the inner wall of the boundary trench  114 T, and upper portions of the buried insulation layer  114 A, the insulation liner  114 B, and the gap-fill insulation layer  114 C may be planarized, thereby forming the boundary structure  114 . 
     In some example embodiments, the buried insulation layer  114 A may be formed through one or more of an atomic layer deposition (ALD) process, a chemical vapor deposition (CVD) process, a plasma enhanced CVD (PECVD) process, a low pressure CVD (LPCVD) process, etc. In some example embodiments, the process for forming the buried insulation layer  114 A may be performed at the same stage as at least some stages of the process for forming the device isolation layer  112 , but inventive concepts are not limited thereto. In some example embodiments, the process for forming the buried insulation layer  114 A may be separately performed after the process of forming the device isolation layer  112 . 
     In some example embodiments, the insulation liner  114 B may be formed by using silicon nitride through an ALD process, a CVD process, a PECVD process, an LPCVD process, etc. The gap-fill insulation layer  114 C may be formed to fill the boundary trench  114 T on the insulation liner  114 B. The gap-fill insulation layer  114 C may be formed to have a thickness sufficient to completely fill the remaining portion inside the boundary trench  114 T. 
     In some example embodiments, the gap-fill insulation layer  114 C may include a silicon oxide such as Tonen Silazene (TOSZ), undoped silicate glass (USG), boro-phospho-silicate glass (BPSG), phosphosilicate glass (PSG), flowable oxide (FOX), plasma enhanced deposition of tetra-ethyl-ortho-silicate (PE-TEOS), or fluoride silicate glass (FSG). 
     Referring to  FIG.  11   , a mask pattern (not shown) may be formed on the substrate  110 , and a portion of the cell array area MCA of the substrate  110  may be removed by using the mask pattern as an etch mask, thereby forming the word line trench  120 T. 
     The word line trench  120 T may be disposed to extend from the cell array area MCA to a portion of the boundary area BA. For example, the mask pattern for forming the word line trench  120 T may be formed by using a double patterning technique (DPT) or a quadruple patterning technique (QPT), but inventive concepts are not limited thereto. 
     Thereafter, the gate dielectric layer  122 , the gate electrode  124 , and the capping insulation layer  126  may be sequentially formed in the word line trench  120 T. 
     For example, the gate dielectric layer  122  may be conformally disposed on the inner wall of the word line trench  120 T. The gate electrode  124  may be formed by filling the word line trench  120 T with a conductive layer (not shown) and then etching back the upper portion of the conductive layer to expose the upper portion of the word line trench  120 T again. The capping insulation layer  126  may be formed by filling the remaining portion of the word line trench  120 T with an insulation material and planarizing the insulation material until the top surface of the buried insulation layer  114 A is exposed. 
     Referring to  FIG.  12   , the buffer layer  118  may be formed on the cell array area MCA and the boundary area BA. The buffer layer  118  may cover the top surface of the first active area AC 1  in the cell array area MCA, and the top surface of the second active area AC 2  may not be covered by the buffer layer  118  in the peripheral circuit area PCA. 
     Thereafter, the gate dielectric layer  116  may be formed on the substrate  110  in the peripheral circuit area PCA. The gate dielectric layer  116  may be formed through one or more of a thermal oxidation process, an ALD process, a CVD process, a PECVD process, an LPCVD process, etc. 
     Thereafter, a portion of the buffer layer  118  covering the cell array area MCA may be removed, thereby leaving the buffer layer  118  on the boundary area BA. The buffer layer  118  may cover the first active area AC 1  and the top surface of the device isolation layer  112  in edge areas of the cell array area MCA and may extend onto the boundary structure  114 . 
     In some example embodiments, a recess process may be performed on the top surface of the device isolation layer  112  exposed in the cell array area MCA, such that the top surface of the first active area AC 1  is located at a higher level than the top surface of the device isolation layer  112  and a portion of the sidewall of the first active area AC 1  is exposed. However, inventive concepts are not limited thereto. 
     Referring to  FIG.  13   , a conductive layer  132  may be formed on the buffer layer  118  in the cell array area MCA and on the gate dielectric layer  116  and the device isolation layer  112  in the peripheral circuit area PCA. In some example embodiments, the conductive layer  132  may include Si, Ge, W, WN, Co, Ni, Al, Mo, Ru, Ti, TiN, Ta, TaN, Cu, or a combination thereof. For example, the conductive layer  132  may include polysilicon such as doped polysilicon. 
     Thereafter, an intermediate layer  134  may be formed on the conductive layer  132 , and a metal layer  136  may be formed on the intermediate layer  134 . The intermediate layer  134  and the metal layer  136  may be formed on the entire areas of the cell array area MCA and the peripheral circuit area PCA. In some example embodiments, the intermediate layer  134  and the metal layer  136  may include TiN, TiSiN. W, tungsten silicide, or a combination thereof. 
     Referring to  FIG.  14   , a mask pattern (not shown) may be formed on the metal layer  136 , and the metal layer  136 , the intermediate layer  134 , and the conductive layer may be patterned in the cell array area MCA by using the mask pattern as an etching mask, thereby forming the cell pad structures  130 . 
     In some example embodiments, the cell pad structures  130  may have a regular grid arrangement and/or matrix arrangement in which the cell pad structures  130  are arranged to be spaced apart from one another in the first horizontal direction X and the second horizontal direction Y. The metal layer  136  may remain on the peripheral circuit area PCA. 
     The outermost cell pad structure  130  from among the cell pad structures  130  may extend onto the boundary area BA. The cell pad structure  130  disposed on the boundary area BA may be referred to as a cell pad extension  130 _E. The cell pad extension  130 _E may include a first portion  130 P 1  and a second portion  130 P 2 . The first portion  130 P 1  may be disposed on the first active area AC 1  and the device isolation layer  112 , and the second portion  130 P 2  may be disposed on the buffer layer  118 . Due to the thickness of the buffer layer  118 , the second portion  130 P 2  may have the top surface disposed at a higher level than the top surface of the first portion  130 P 1 . 
     Thereafter, the insulation pattern  152  surrounding the sidewalls of the cell pad structures  130  may be formed. The insulation pattern  152  may be formed by using silicon nitride. 
     Referring to  FIG.  15   , the insulation layer  154  may be formed on the cell pad structures  130 , the top surface of the insulation pattern  152 , and on the metal layer  136 . The insulation layer  154  may be formed by using silicon nitride. 
     Thereafter, a mask pattern (not shown) may be formed on the insulation layer  154 , and some of the cell pad structures  130  may be removed to re-expose the first active area AC 1  of the substrate  110 . Thereafter, the upper portion of the exposed substrate  110  may be further removed, thereby forming a direct contact hole DCH. 
     Thereafter, the direct contact spacer DCS may be formed on the inner wall of the direct contact hole DCH. For example, the direct contact spacer DCS may be formed by using silicon nitride or silicon oxide. 
     A conductive layer (not shown) may be formed inside the direct contact hole DCH, and the upper portion of the conductive layer may be etched back until the top surface of the insulation layer  154  is exposed, thereby forming the direct contact DC inside the direct contact hole DCH. 
     Referring to  FIG.  16   , the bit line conductive layer  138  covering the direct contact DC and the insulation layer  154  may be formed. The bit line conductive layer  138  may include at least one of ruthenium (Ru), tungsten (W), cobalt (Co), titanium (Ti), and titanium nitride (TiN). 
     In some example embodiments, the bit line conductive layer  138  may be formed by using a material different from a material included in the metal layer  136 . However, inventive concepts are not limited thereto, and the bit line conductive layer  138  may be formed by using the same material as the material included in the metal layer  136 . 
     Referring to  FIG.  17   , the insulation layer  154  and the bit line conductive layer  138  may be removed from the peripheral circuit area PCA and the boundary area BA. 
     Thereafter, a first insulation capping layer  142  may be formed on the metal layer  136  in the peripheral circuit area PCA and on the bit line conductive layer  138  in the cell array area MCA. 
     Referring to  FIG.  18   , a mask pattern (not shown) may be formed on the first insulation capping layer  142 , and the first insulation capping layer  142 , the metal layer  136 , the intermediate layer  134 , and the conductive layer  132  may be patterned in the peripheral circuit area PCA by using the mask pattern, thereby forming the gate capping pattern  142 B and the peripheral circuit gate electrode PGS. 
     In some example embodiments, the peripheral circuit gate electrode PGS may include the second conductive layer  132 B, the second intermediate layer  134 B, and the second metal layer  136 B sequentially arranged on the gate dielectric layer  116 . 
     Thereafter, an insulation spacer  150 B covering the sidewall of the peripheral circuit gate electrode PGS may be formed. The insulation spacer  150 B may be formed by using silicon nitride. 
     In the process of forming the insulation spacer  150 B, a spacer  150 _E may also be disposed on the sidewall of the cell pad extension  130 _E disposed in the boundary area BA. 
     Thereafter, a passivation layer  146  covering the gate capping pattern  142 B and sidewalls of the peripheral circuit gate electrode PGS is formed in the peripheral circuit area PCA. An insulation layer (not shown) may be formed on the passivation layer  146  to completely cover the gate capping pattern  142 B and the peripheral circuit gate electrode PGS, and the upper portion of the insulation layer may be planarized until the top surface of the gate capping pattern  142 B is exposed, thereby forming the first interlayer insulation layer  148 . 
     Referring to  FIGS.  19 A and  19 B , a second insulation capping layer  144  may be formed on the first insulation capping layer  142  in the cell array area MCA and on the first interlayer insulation layer  148  in the peripheral circuit area PCA. 
     Thereafter, the second insulation capping layer  144 , the first insulation capping layer  142 , and the bit line conductive layer  138  may be patterned in the cell array area MCA, thereby forming the insulation capping structures  140  and the bit lines BL. 
     In the process of forming the bit line BL, an upper portion of the direct contact spacer DCS disposed inside the direct contact hole DCH may be removed at the same time, and thus the top surface of the direct contact spacer DCS may be located at a level lower than that of the top surface of the direct contact DC. 
     In the process of forming the bit line BL, a portion of the bit line conductive layer  138  may remain on the boundary area BA, and the portion may be referred to as the edge conductive layer BL_E. 
     Thereafter, the bit line spacer  150 A may be formed on the sidewall of a bit line structure BLS, and the insulation fences  156  may be formed between the bit lines BL. 
     Referring to  FIG.  20   , the second insulation capping layer  144  and the first interlayer insulation layer  148  are etched in the peripheral circuit area PCA, thereby forming a plurality of contact holes CPH exposing the second active areas AC 2  of the substrate  110 . Thereafter, the insulation layer  154  exposed between the bit lines BL is removed in the cell array area MCA, thereby exposing the top surface of the cell pad structure  130 . 
     Thereafter, a conductive barrier film  162  and a conductive layer  164  covering the exposed surface of the substrate  110  in the cell array area MCA and the peripheral circuit area PCA are formed. By patterning the conductive barrier film  162  and the conductive layer  164 , the landing pads LP including the conductive barrier film  162 A and the landing pad conductive layer  164 A are formed in the cell array area MCA, and a plurality of contact plugs CP including the conductive barrier film  162 B and the landing pad conductive layer  164 B are formed in the peripheral circuit area PCA. 
     Referring now to  FIG.  21   , the insulation pattern  166  covering the landing pads LP may be formed in the cell array area MCA, and the second etch stop layer  174  covering the contact plugs CP may be formed in the peripheral circuit area PCA. 
     Thereafter, the first etch stop layer  172  may be formed on the cell array area MCA. 
     The lower electrodes  182 , which penetrate through the first etch stop layer  172  and are connected to the landing pads LP, may be formed, and the capacitor dielectric layer  184  and the upper electrode  186  may be sequentially formed on the sidewalls of the lower electrodes  182 . 
     Thereafter, the second interlayer insulation layer  190  covering the upper electrode  186  may be formed on the cell array area MCA and the peripheral circuit area PCA. 
     The semiconductor device  100  may be completed by performing the above-described method. 
     In general or typically, the peripheral circuit gate electrode PGS is formed to have the same stack configuration as that of the bit line BL. For example, the peripheral circuit gate electrode PGS is formed, such that the bit line BL and a metal layer included in the peripheral circuit gate electrode PGS include the same material and/or have the same height. However, in a process for patterning the bit line BL, it becomes difficult to precisely control a patterning process due to a step or a level difference of the top surface of the cell pad extension  130 _E disposed in the boundary area BA, and thus a process defect may occur. 
     However, according to some example embodiments, the cell pad structure  130  and the peripheral circuit gate electrode PGS may be formed to have the same stack configuration. Therefore, a process defect due to a step or a level difference of the top surface of the cell pad extension  130 _E disposed in the boundary area BA may be prevented or reduced in likelihood of and/or impact from occurrence. Alternatively or additionally, since a material included in the bit line BL may be selected independently from a material constituting the peripheral circuit gate electrode PGS, performance improvement and/or flexibility and/or optimization of the semiconductor device  100  may be implemented. 
     In other embodiments, in the process described with reference to  FIG.  15   , the insulation layer  154  formed on the peripheral circuit area PCA may be removed, and then the bit line conductive layer  138  may be formed directly on the metal layer  136 . In this case, the semiconductor device  100 A described with reference to  FIGS.  7  to  9    may be formed. 
     When the terms “about” or “substantially” are used in this specification in connection with a numerical value, it is intended that the associated numerical value includes a manufacturing or operational tolerance (e.g., ±10%) around the stated numerical value. Moreover, when the words “generally” and “substantially” are used in connection with geometric shapes, it is intended that precision of the geometric shape is not required but that latitude for the shape is within the scope of the disclosure. Moreover, when the words “generally” and “substantially” are used in connection with material composition, it is intended that exactitude of the material is not required but that latitude for the material is within the scope of the disclosure. 
     Further, regardless of whether numerical values or shapes are modified as “about” or “substantially,” it will be understood that these values and shapes should be construed as including a manufacturing or operational tolerance (e.g., ±10%) around the stated numerical values or shapes. Thus, while the term “same,” “identical,” or “equal” is used in description of example embodiments, it should be understood that some imprecisions may exist. Thus, when one element or one numerical value is referred to as being the same as another element or equal to another numerical value, it should be understood that an element or a numerical value is the same as another element or another numerical value within a desired manufacturing or operational tolerance range (e.g., ±10%). 
     While inventive concepts have been particularly shown and described with reference to embodiments thereof, it will be understood that various changes in form and details may be made therein without departing from the spirit and scope of the following claims. Furthermore example embodiments are not necessarily mutually exclusive. For example, some example embodiments may include one or more features described with reference to one or more figures, and may also include one or more other features described with reference to one or more other figures.