Patent Publication Number: US-2021175173-A1

Title: Semiconductor device

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     Korean Patent Application No. 10-2019-0163653, filed on Dec. 10, 2019, in the Korean Intellectual Property Office, and entitled: “Semiconductor Device,” is incorporated by reference herein in its entirety. 
     BACKGROUND 
     1. Field 
     Example embodiments relate to a semiconductor device, and more particularly, to a semiconductor device including a stack structure having a flat region in a connection region adjacent to a memory cell array region. 
     2. Description of the Related Art 
     A semiconductor device may include gate electrodes stacked from a surface of a semiconductor substrate in a vertical direction. To implement high integration density of such a semiconductor device, the number of stacked gate electrodes may be increased. 
     SUMMARY 
     According to an example embodiment, a semiconductor device includes a lower structure, a stack structure disposed in a memory cell array region on the lower structure and extending from the memory cell array region into a connection region, an upper insulating layer on the stack structure, gate contact plugs in the connection region, and a memory vertical structure penetrating through the stack structure in the memory cell array region, wherein the stack structure includes a plurality of interlayer insulating layers and a plurality of horizontal layers, wherein the plurality of interlayer insulating layers and the plurality of horizontal layers are alternately stacked in the memory cell array region on the lower structure, and extends into the connection region on the lower structure adjacent to the memory cell array region, wherein, in the connection region, a first cross-sectional structure of the stack structure includes a first gate staircase region and a first gate flat region adjacent to the first gate staircase region, wherein the first gate staircase region includes first gate pads lowering in a first horizontal direction by a first height therebetween, wherein the first horizontal direction is directed to the connection region in the memory cell array region, wherein the first gate flat region includes a first gate flat pad region, a first gate flat edge region, and a first gate flat dummy region disposed between the first gate flat pad region and the first gate flat edge region, and wherein the gate contact plugs include a plurality of first gate contact plugs in contact with the first gate pads on the first gate pads, a plurality of flat contact plugs in contact with the first gate flat pad region on the first gate flat pad region, and an edge flat contact plug in contact with the first gate flat edge region on the first gate flat edge region. 
     According to an example embodiment, a semiconductor device includes a lower structure, a stack structure disposed in a memory cell array region on the lower structure and extending from the memory cell array region into a connection region, gate contact plugs on the stack structure in the connection region, and a memory vertical structure penetrating through the stack structure in the memory cell array region, wherein the stack structure includes a plurality of interlayer insulating layers and a plurality of horizontal layers alternately stacked, wherein, in the connection region, the stack structure includes a staircase region and a flat region adjacent to the staircase region, wherein the staircase region includes pads lowered in a first horizontal direction, wherein the flat region includes a flat pad region, a flat edge region, and a flat dummy region disposed between the flat pad region and the flat edge region, and wherein the gate contact plugs include first gate contact plugs on the pads, a plurality of flat contact plugs on the flat pad region, and a flat edge contact plug on the flat edge region. 
     According to an example embodiment, a semiconductor device includes a lower structure, a stack structure disposed in a memory cell array region on the lower structure and extending from the memory cell array region into a connection region, gate contact plugs on the stack structure, and a memory vertical structure penetrating through the stack structure in the memory cell array region, wherein the stack structure includes a lower stack structure and an upper stack structure on the lower stack structure, wherein the lower stack structure includes a plurality of lower horizontal layers stacked and spaced apart from each other in a vertical direction, wherein the vertical direction is perpendicular to an upper surface of the lower structure, wherein the upper stack structure includes a plurality of upper horizontal layers stacked and spaced apart from each other in the vertical direction, wherein the plurality of upper horizontal layers include a first staircase region including first pads lowered in the connection region by a first height therebetween, wherein the lower horizontal layers include a second staircase region including second pads lowered by a second height smaller than the first height, wherein the upper stack structure includes a first flat region adjacent to the first staircase region, wherein the lower stack structure includes a second flat region adjacent to the second staircase region, wherein each of the first pads has a first length, wherein the first flat region includes a flat pad region having a second length greater than the first length in a first horizontal direction, a flat edge region having a third length greater than the first length in the first horizontal direction, and a flat dummy region disposed between the flat pad region and the flat edge region, wherein the a fourth length of the flat dummy region in the first horizontal direction is greater than each of the second length and the third length, wherein the second flat region has a length greater than the first length in the first horizontal direction, and wherein the gate contact plugs include a plurality of first gate contact plugs on first and second pads, a second gate contact plug and a dummy contact plug spaced apart from each other on the flat pad region, and a flat edge contact plug on the flat edge region. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
       Features will become apparent to those of skill in the art by describing in detail exemplary embodiments with reference to the attached drawings, in which: 
         FIGS. 1A to 5B  are diagrams illustrating a semiconductor device according to an example embodiment; 
         FIG. 6  is a cross-sectional diagram illustrating an example of a portion of elements of a semiconductor device according to an example embodiment; 
         FIGS. 7A and 7B  are enlarged cross-sectional diagrams illustrating a modified example of a semiconductor device according to an example embodiment; 
         FIG. 8  is a plan diagram illustrating a modified example of a semiconductor device according to an example embodiment; 
         FIGS. 9 to 10B  are diagrams illustrating a modified example of a semiconductor device according to an example embodiment; and 
         FIGS. 11A to 12C  are diagrams illustrating an example of stages in a method of manufacturing a semiconductor device according to an example embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     Hereinafter, embodiments will be described as follows with reference to the accompanying drawings. 
     In the description below, a planar structure of a semiconductor device will be described with reference to  FIGS. 1A and 1B .  FIGS. 1A and 1B  are plan diagrams illustrating a semiconductor device according to an example embodiment, and  FIG. 1A  illustrates a plan diagram illustrating a portion of the elements illustrated in  FIG. 1B . 
     Referring to  FIGS. 1A and 1B , a memory cell array region MA and a connection region EA adjacent to the memory cell array region MA, e.g., along the first horizontal direction X, may be provided. A stack structure ST′ may be disposed in the memory cell array region MA and may extend into the connection region EA. The stack structure ST′ may include a gate region GA and an insulating region IA. An internal region indicated by a dashed line in  FIGS. 1A and 1B  refers to the insulating region IA, e.g., a portion of the dashed line denoted as “IA” in  FIGS. 1A and 1B  and facing the gate region GA may be understood as a boundary with the gate region GA. The insulating region IA may be disposed in the connection region EA. The insulating region IA may be spaced apart from the memory cell array region MA. 
     A plurality of separation structures  62 B,  62 S 1 , and  62 S 2  may be disposed. The plurality of separation structures  62 B,  62 S 1 , and  62 S 2  may include block separation structures  62 B, first auxiliary separation structures  62 S 1  and second auxiliary separation structures  62 S 2 . The plurality of separation structures  62 B,  62 S 1 , and  62 S 2  may be formed of the same material. 
     For example, each of the plurality of separation structures  62 B,  62 S 1 , and  62 S 2  may be formed of an insulating material, e.g., silicon oxide, or the like. In another example embodiment, each of the plurality of separation structures  62 B,  62 S 1 , and  62 S 2  may be configured to include a conductive material and an insulating material between the conductive material and the stack structure ST′. 
     The block separation structures  62 B may, e.g., continuously, cross the memory cell array region MA and the connection region EA in the first horizontal direction X, and may separate, e.g., each of, the memory cell array region MA and the connection region EA in a second horizontal direction Y perpendicular to the first horizontal direction X. 
     The first auxiliary separation structures  62 S 1  may cross the memory cell array region MA and may, e.g., partially, extend into the connection region EA. The second auxiliary separation structures  62 S 2  may be spaced apart from the memory cell array region MA, and may be disposed in the connection region EA. The first and second auxiliary separation structures  62 S 1  and  62 S 2  may be disposed between, e.g., adjacent ones of, the block separation structures  62 B. 
     The block separation structures  62 B may include a first block separation structure  62 B 1 , a second block separation structure  62 B 2 , and a third block separation structure  62 B 3  arranged in order, e.g., sequentially, in the second horizontal direction Y. 
     The first auxiliary separation structures  62 S 1  may be disposed between the first block separation structure  62 B 1  and the second block separation structure  62 B 2  and may be disposed between the second block separation structure  62 B 2  and the third block separation structure  62 B 3 . In an example embodiment, the second auxiliary separation structures  62 S 2  may not be disposed between the first block separation structure  62 B 1  and the second block separation structure  62 B 2 , and may be disposed between the second block separation structure  62 B 2  and the third block separation structure  62 B 3 . 
     In an example embodiment, an insulating separation pattern  34  (in  FIG. 1B ) may be disposed between separation structures of the second block separation structures  62 B 2  and the first auxiliary separation structures  62 S 1 , the separation structures adjacent to each other in the second horizontal direction Y. The insulating separation pattern  34  (in  FIG. 1B ) may cross the memory cell array region MA and may extend into the connection region EA. 
     The insulating region IA may be disposed, e.g., only, in the connection region EA, e.g., among the memory cell array region MA and the connection region EA. In the stack structure ST′, a region other than the insulating region IA may be defined as the gate region GA. For example, in the connection region EA, a region other that the insulating region IA (e.g., which is indicated with dashed frames in  FIGS. 1A and 1B ) is the gate region GA, e.g., portions of the connections region EA between adjacent dashed frames are parts of the gate region GA. 
     In an example embodiment, the insulating region IA may be disposed between the first block separation structure  62 B 1  and the second block separation structure  62 B 2 , and may not be disposed between the second block separation structure  62 B 2  and the third block separation structure  62 B 3 . The insulating region IA may be spaced apart from the first auxiliary separation structures  62 S 1  and the insulating separation pattern  34  (in  FIG. 1B ). In an example embodiment, each of the block separation structures  62 B may be disposed between the insulating region IA and the second auxiliary separation structures  62 S 2  adjacent to each other in the second horizontal direction Y. 
     In the connection region EA, the stack structure ST′ may have a staircase structure. In the connection region EA, the stack structure ST′ may include a plurality of flat regions FAa, FAb, and FAc. For example, the stack structure ST′ may include an upper flat region FAa, one or a plurality of intermediate flat regions FAb, and a lower flat region FAc disposed in order, e.g., sequentially, in a direction oriented away from the memory cell array region MA along the first horizontal direction X. 
     In the description below, a semiconductor device will be described with reference to  FIGS. 1C, 1D, and 2A to 3B  along with  FIGS. 1A and 1B .  FIG. 1C  is an enlarged plan diagram of portion “A” in  FIG. 1B ,  FIG. 1D  is an enlarged plan diagram of portion “B” in  FIG. 1B ,  FIG. 2A  is a cross-sectional diagram along line I-I′ in  FIG. 1B ,  FIG. 2B  is an enlarged diagram of portion “C” in  FIG. 2A ,  FIG. 3A  is a cross-sectional diagram along line II-IF in  FIG. 1B , and  FIG. 3B  is an enlarged diagram of portion “D” illustrated in  FIG. 3A . 
     Referring to  FIGS. 1A to 3B , an integrated circuit region  7  may be disposed on a lower substrate  5 . The lower substrate  5  may be configured as a semiconductor substrate (e.g., a single crystalline silicon substrate). The integrated circuit region  7  may include circuit wirings  8  and a lower insulating layer  9  covering the circuit wirings  8 . The circuit wirings  8  may include peripheral contact pads  8 P. An upper substrate  12  may be disposed on the integrated circuit region  7 . The upper substrate  12  may include, e.g., polysilicon. A gap-fill insulating layer  13  penetrating through the upper substrate  12  may be disposed. In an example embodiment, the gap-fill insulating layer  13  may be formed of an insulating material, e.g., silicon oxide. A lower structure  3  may include the lower substrate  5 , the integrated circuit region  7 , the upper substrate  12  and the gap-fill insulating layer  13 . 
     For example, a plurality of the gap-fill insulating layers  13  may be disposed under the insulating region IA disposed between a pair of block separation structures  62 B adjacent to each other. In another example, the gap-fill insulating layer  13  may be configured to have a line shape extending in the first horizontal direction X under the insulating region IA disposed between the pair of block separation structures  62 B adjacent to each other. 
     The memory cell array region MA and the connection region EA may be defined on the upper substrate  12 . The stack structure ST′ may be disposed in the memory cell array region MA on the upper substrate  12 , and may extend into the connection region EA on the upper substrate  12 . The first horizontal direction X may be in parallel to an upper surface of the upper substrate  12 . 
     A first upper insulating layer  33  may be disposed on the stack structure ST′. A memory vertical structure  36  penetrating through the first upper insulating layer  33  and the stack structure ST′ may be disposed. A second upper insulating layer  53  may be disposed on the first upper insulating layer  33 . The plurality of separation structures  62 B,  62 S 1 , and  62 S 2  may penetrate through the second upper insulating layer  53 , the first upper insulating layer  33 , and the stack structure ST′. A third upper insulating layer  65  may be disposed on the second upper insulating layer  53 . A bit line contact plug  72  penetrating through the second and third upper insulating layers  53  and  65  and electrically connected to the memory vertical structure  36  may be disposed. A bit line  74   b  may be disposed on the bit line contact plug  72 . The first to third upper insulating layers  33 ,  53 , and  65  may be formed of an insulating material, e.g., silicon oxide, or the like. 
     The stack structure ST′ may include interlayer insulating layers  20  and horizontal layers  23  alternately stacked. The interlayer insulating layers  20  and the horizontal layers  23  may be alternately stacked in a vertical direction Z in the memory cell array region MA, and may extend from the memory cell array region MA into the connection region EA. The vertical direction Z may be perpendicular to an upper surface of the lower structure  3 . The horizontal layers  23  may include pad regions formed in a staircase shape in the connection region EA. 
     The stack structure ST′ may include a lower stack structure ST 1 ′ and an upper stack structure ST 2 ′ disposed on the lower stack structure ST 1 ′. 
     The lower stack structure ST 1 ′ may include a first interlayer insulating layer  20   a  and lower horizontal layers  23 Ga and  23 Ia alternately stacked. A lowermost layer of the first interlayer insulating layer  20   a  and the lower horizontal layers  23 Ga and  23 Ia may be a lower interlayer insulating layer, and an uppermost layer may be a lower horizontal layer. The lower stack structure ST 1 ′ may further include a second interlayer insulating layer  20   b  covering the first interlayer insulating layer  20   a  and the lower horizontal layers  23 Ga and  23 Ia. 
     The upper stack structure ST 2 ′ may include a plurality of horizontal layers  23 G and  23 I stacked and spaced apart from each other in the vertical direction Z. The upper stack structure ST 2 ′ may further include a plurality of third interlayer insulating layers  20   c  alternately stacked with the plurality of horizontal layers  23 G and  23 I. The interlayer insulating layers  20  may include first to third interlayer insulating layers  20   a ,  20   b , and  20   c . The interlayer insulating layers  20  may be formed of an insulating material, e.g., silicon oxide. 
     The plurality of horizontal layers  23 G and  23 I may include a plurality of intermediate horizontal layers  23 Gb and  23 Ib, upper horizontal layers  23 Gc disposed on the plurality of intermediate horizontal layers  23 Gb and  23 Ib, and floating horizontal layers  23 Gf and  23 If disposed on the plurality of intermediate horizontal layers  23 Gb and  23 Ib. The horizontal layers  23  may include the lower horizontal layers  23 Ga and  23 Ia, the intermediate horizontal layers  23 Gb and  23 Ib, the upper horizontal layers  23 Gc, and the floating horizontal layers  23 Gf and  23 If. 
     The intermediate horizontal layers  23 Gb and  23 Ib may be stacked and spaced apart from each other in the vertical direction Z in the memory cell array region MA and may extend into the connection region EA. The upper horizontal layers  23 Gc may be stacked and spaced apart from each other in the vertical direction Z in the memory cell array region MA and may extend into the connection region EA. 
     Each of the upper horizontal layers  23 Gc may have a length shorter than a length of each of the intermediate horizontal layers  23 Gb and  23 Ib in the first horizontal direction X. The floating horizontal layers  23 Gf and  23 If may be stacked and spaced apart from each other in the vertical direction Z in the connection region EA. The floating horizontal layers  23 Gf and  23 If may face the upper horizontal layers  23 Gc, e.g., each of the floating horizontal layers  23 Gf and  23 If may be at a same level as and face a corresponding one of the upper horizontal layers  23 Gc with a predetermined distance therebetween. 
     In the stack structure ST′, the horizontal layers  23  disposed in the gate region GA may be gate horizontal layers  23 G, and the horizontal layers  23  disposed in the insulating region IA may be insulating horizontal layers  23 I. Accordingly, the gate horizontal layers  23 G and the insulating horizontal layers  23 I may be in contact with each other at a boundary between the gate region GA and the insulating region IA disposed in the connection region EA, e.g., each of the insulating horizontal layers  23 I may directly contact a corresponding one of the gate horizontal layers  23 G at the boundary between the gate region GA and the insulating region IA and extend therefrom along the first horizontal direction X in the insulating region IA. For example, referring to  FIGS. 1B, 2A, and 3A , the insulating horizontal layers  23 I may directly extend from corresponding ones of the gate horizontal layers  23 G in both the lower and upper stack structure ST 1 ′ and ST′ 2  only at the insulating region IA of the connection region EA, e.g., the gate horizontal layers  23 G may extend in the connection region EA in parallel to the insulating horizontal layers  23 I between adjacent insulating regions IA (e.g., between the dashed regions of  FIG. 1A ). 
     Lower horizontal layers of the horizontal layers  23  disposed in the gate region GA may be lower gate horizontal layers  23 Ga, and lower horizontal layers of the horizontal layers  23  disposed in the insulating region IA may be lower insulating horizontal layers  23 Ia. Similarly, intermediate horizontal layers of the horizontal layers  23  disposed in the gate region GA may be intermediate gate horizontal layers  23 Gb, and intermediate horizontal layers of the horizontal layers  23  disposed in the insulating region IA may be intermediate insulating horizontal layers  23 Ib. The upper horizontal layers  23 Gc may be disposed in the gate region GA, and may be upper gate horizontal layers. In the description below, the upper horizontal layers  23 Gc are referred to as upper gate horizontal layers. Floating horizontal layers of the horizontal layers  23  may include floating gate horizontal layers  23 Gf disposed in the gate region GA ( FIG. 2A ), and floating insulating horizontal layers  23 If disposed in the insulating region IA ( FIG. 3A ). 
     The gate horizontal layers  23  may include the gate horizontal layers  23 G and the insulating horizontal layers  23 I. The gate horizontal layers  23 G may include the lower gate horizontal layers  23 Ga, the intermediate gate horizontal layers  23 Gb, the upper gate horizontal layers  23 Gc, and the floating gate horizontal layers  23 Gf. The insulating horizontal layers  23 I (in  FIG. 3A ) may include the lower insulating horizontal layers  23 Ia, the intermediate insulating horizontal layers  23 Ib, and the floating gate horizontal layers  23 Gf. 
     In an example embodiment, the insulating horizontal layers  23 I may be formed of an insulating material having etch selectivity with respect to the interlayer insulating layers  20 , e.g., formed of silicon nitride. In an example embodiment, the gate horizontal layers  23 G may include a conductive material. 
     Referring to  FIG. 2A , the gate horizontal layers  23 G may include pad regions formed in a staircase shape in the connection region EA. 
     The intermediate gate horizontal layers  23 Gb may include intermediate gate pads GPb lowering in the first horizontal direction X with a difference of a first length therebetween and first lower gate pads GPc 1  lowering in the first horizontal direction X with a difference of a second length therebetween. The second length may be smaller than the first length. 
     The upper gate horizontal layers  23 Gc may include upper gate pads GPc lowering in order with a difference of the second length in the first horizontal direction X, and floating gate horizontal layers  23 Gf may include floating gate pads GPf lowering in order with a difference of the second length in the first horizontal direction X. The lower gate horizontal layers  23 Ga may include second lower gate pads GPc 2  lowering in order with a difference of the second length in the first horizontal direction X. Accordingly, the first length between the intermediate gate pads GPb adjacent to each other may be greater than the second length between the second lower gate pads GPc 2  adjacent to each other. 
     A region in which the upper gate pads GPa are formed may be defined as an upper gate staircase region GSa, a region in which the floating gate pads GPf are formed may be defined as a floating gate staircase region GSf, a region in which the intermediate gate pads GPb are formed may be defined as an intermediate gate staircase region GSb, a region in which the first lower gate pads GPc 1  are formed may be defined as a first lower gate staircase region GSc 1 , and a region in which the second lower gate pads GPc 2  are formed may be defined as a second lower gate staircase region GSc 2 . 
     The gate region GA of the stack structure ST′ may include gate flat regions GFa, GFb, and GFc. The gate flat regions GFa, GFb, and GFc may include an upper gate flat region GFa, an intermediate gate flat region GFb, and a lower gate flat region GFc disposed in order in the first horizontal direction X. 
     The upper gate flat region GFa may be disposed between the floating gate staircase region GSf and the intermediate gate staircase region GSb. The upper gate flat region GFa (in  FIGS. 1C and 2A ) may include an upper gate flat dummy region GFd 1  (in  FIGS. 1C and 2A ) and an upper gate flat edge region GFe 1  (in  FIGS. 1C and 2A ). The lower gate flat region GFc may be disposed between the first lower gate staircase region GSc 1  and the second lower gate staircase region GSc 2 . 
     In an example embodiment, a first dummy pattern  24   dc  may be disposed between the lower gate flat region GFc and the first lower gate staircase region GSc 1 . The first dummy pattern  24   dc  may be disposed on the second interlayer insulating layer  20   b . In an example embodiment, the first dummy pattern  24   dc  may be formed of a conductive material. 
     A plurality of the intermediate gate staircase regions GSb may be disposed. In an example embodiment, a plurality of the intermediate gate flat regions GFb may be disposed. One of the intermediate gate flat regions GFb may be disposed between intermediate gate staircase regions GSb adjacent each other among the intermediate gate staircase regions GSb. Accordingly, one or a plurality of the intermediate gate flat regions GFb may be disposed. The intermediate gate staircase regions GSb may be disposed in order in the first horizontal direction X, and may include a first gate staircase region GSb and a second gate staircase region GSb disposed in order in the first horizontal direction X and having substantially the same cross-sectional structure, and one of the first gate staircase regions GSb may be disposed between the first gate staircase region GSb and the second gate staircase region GSb. 
     In the description below, the intermediate gate flat region GFb will be described with reference to  FIGS. 1D and 2B . 
     Referring to  FIGS. 1D and 2B , each of the intermediate gate pads GPb may have a first length La in the first horizontal direction X. The intermediate gate flat region GFb may include an intermediate gate flat pad region GFp 2 , an intermediate gate flat edge region GFe 2 , and an intermediate gate flat dummy region GFd 2  disposed between the intermediate gate flat pad region GFp 2  and the intermediate gate flat edge region GFe 2 . The intermediate gate flat pad region GFp 2 , the intermediate gate flat dummy region GFd 2 , and the intermediate gate flat edge region GFe 2  may be disposed in order, e.g., sequentially, in the first horizontal direction X. 
     The intermediate gate flat pad region GFp 2  may have a second length Lp greater than the first length La in the first horizontal direction X. The intermediate gate flat edge region GFe 2  may have a third length Lc greater than the first length La in the first horizontal direction X. The intermediate gate flat dummy region GFd 2  may have a fourth length Ld greater than each of the second length Lp and the third length Lc in the first horizontal direction X. 
     In an example embodiment, the second length Lp of the intermediate gate flat pad region GFp 2  may be greater than the third length Lc of the intermediate gate flat edge region GFe 2 . In another example embodiment, the third length Lc of the intermediate gate flat edge region GFe 2  may be the same as the second length Lp of the intermediate gate flat pad region GFp 2 . Accordingly, the second length Lp of the intermediate gate flat pad region GFp 2  may be the same as or greater than the third length Lc of the intermediate gate flat edge region GFe 2 . 
     In an example embodiment, the fourth length Ld of the intermediate gate flat dummy region GFd 2  may be greater than a sum of the second length Lp of the intermediate gate flat pad region GFp 2  and the third length Lc of the intermediate gate flat edge region GFe 2 . In another example embodiment, the fourth length Ld of the intermediate gate flat dummy region GFd 2  may be the same as a sum of the second length Lp of the intermediate gate flat pad region GFp 2  and the third length Lc of the intermediate gate flat edge region GFe 2 . Accordingly, the fourth length Ld may be the same as or greater than a sum of the second length Lp and the third length Lc. 
     Each of the gate horizontal layers  23 G may have a first thickness t 1 . Each of the intermediate gate flat pad region GFp 2 , the intermediate gate flat edge region GFe 2 , and the intermediate gate flat dummy region GFd 2  may have a second maximum thickness t 2  greater than the first thickness t 1 . 
     The gate horizontal layers  23 G may include a conductive material. The intermediate gate flat pad region GFp 2  and the intermediate gate flat edge region GFe 2  may include the conductive material. The intermediate gate flat dummy region GFd 2  may not include the conductive material, and may be filled with an insulating material. For example, the intermediate gate flat pad region GFp 2  may include a first conductive layer, the intermediate gate flat edge region GFe 2  may include a second conductive layer, the intermediate gate flat dummy region GFd 2  may include an insulating material, and the insulating material of the intermediate gate flat dummy region GFd 2  may separate the first conductive layer of the intermediate gate flat pad region GFp 2  and the second conductive layer of the intermediate gate flat dummy region GFd 2  from each other in the first horizontal direction X, such that the first conductive layer and the second conductive layer may be spaced apart from each other in the first horizontal direction X. The first conductive layer and the second conductive layer may include the same conducive material. 
     The insulating material of the intermediate gate flat dummy region GFd 2  may be a portion of the first upper insulating layer  33 . Accordingly, the portion of the first upper insulating layer  33  extending to a region between the intermediate gate flat pad region GFp 2  and the intermediate gate flat edge region GFe 2  may be defined as the intermediate gate flat dummy region GFd 2 . 
     Gate contact plugs  70   g   1 ,  70   g   2 ,  70   d   1  and  70   d   2  may be disposed in the connection region EA. In an example embodiment, the gate contact plugs may include first gate contact plugs  70   g   1  on the upper gate pads GPa (in  FIG. 2A ), the intermediate gate pads GPb, the first lower gate pads GPc 1 , and first gate contact plugs  70   g   1  on the second lower gate pads GPc 2 . Gate contact plugs of the first gate contact plugs  70   g   1 , disposed on the intermediate gate pads GPb, may be referred to as first intermediate gate contact plugs. The first gate contact plugs  70   g   1  may be in contact with and electrically connected to the intermediate gate pads GPb on the intermediate gate pads GPb. 
     In an example embodiment, the gate contact plugs may further include a plurality of flat contact plugs  70   g   2  and  70   d   1  in contact with the intermediate gate flat pad region GFp 2  on the intermediate gate flat pad region GFp 2 . The plurality of flat contact plugs  70   g   2  and  70   d   1  may include a second intermediate gate contact plug  70   g   2  and a first dummy gate contact plug  70   d   1  disposed in order in the first horizontal direction X. 
     In an example embodiment, the gate contact plugs may further include an edge flat contact plugs  70   d   2  in contact with the intermediate gate flat edge region GFe 2  on the intermediate gate flat edge region GFe 2 . The edge flat contact plugs  70   d   2  may be referred to as a second dummy gate contact plug  70   d   2 . The first dummy gate contact plug  70   d   1  may prevent deformation or defects of the second intermediate gate contact plug  70   g   2 . The edge flat contact plug  70   d   2  may prevent deformation or defects of the first intermediate gate contact plug  70   g   1  adjacent to the second dummy gate contact plug  70   d   2 . For example, when gate contact holes for forming the first and second intermediate gate contact plugs  70   g   1  and  70   g   2  and dummy contact holes for forming the first and second dummy contact plugs  70   d   1  and  70   d   2  are formed simultaneously, an etching gas of an etching process for forming the dummy contact holes and the gate contact holes may be stably supplied into the gate contact holes, e.g., oriented specifically toward the intermediate gate contact plugs, while being unstably supplied into the dummy contact holes. Accordingly, the first and second intermediate gate contact plugs  70   g   1  and  70   g   2  formed in the gate contact holes may be stably formed without defects, e.g., due to formation of the first and second dummy contact plugs  70   d   1  and  70   d   2 . Accordingly, the first and second dummy contact plugs  70   d   1  and  70   d   2  may improve reliability and/or productivity of the semiconductor device. 
     The gate contact plugs  70   g   1  and  70   g   2 , as well as the dummy contact plugs  70   d   1  and  70   d   2 , may be formed of the same conductive material, such as a doped silicon, a metal nitride (e.g., TiN, WN, or the like) or a metal (e.g., tungsten, or the like). It is noted, however, that while the dummy contact plugs  70   d   1  and  70   d   2  may have a structure and shape identical or similar to that of the gate contact plugs  70   g   1  and  70   g   2 , an electrical signal is not applied to the dummy contact plugs  70   d   1  and  70   d   2 . 
     A spacing distance between the second intermediate gate contact plug  70   g   2  and the first dummy gate contact plug  70   d   1  may be less than a spacing distance between the first dummy gate contact plug  70   d   1  and the intermediate gate flat dummy region GFd 2 , e.g., along the first horizontal direction X. A spacing distance between the second intermediate gate contact plug  70   g   2  and the first dummy gate contact plug  70   d   1  may be substantially the same as a spacing distance between the first and second intermediate gate contact plugs  70   g   1  and  70   g   2 , e.g., when the second intermediate gate contact plug  70   g   2  is between the first intermediate gate contact plug  70   g   1  and the first dummy gate contact plug  70   d   1  (left side of  FIG. 2B ). A spacing distance between the second intermediate gate contact plug  70   g   2  and the first dummy gate contact plug  70   d   1  may be substantially the same as a spacing distance between the second dummy gate contact plug  70   d   2  and the first intermediate gate contact plugs  70   g   1 , e.g., along the first horizontal direction X. To distinguish the first intermediate gate contact plugs  70   g   1  adjacent to the second intermediate gate contact plug  70   g   2  (i.e., left side of  FIG. 2B ) from the first intermediate gate contact plugs  70   g   1  adjacent to the second dummy gate contact plug  70   d   2  (i.e., right side of  FIG. 2B ), the first intermediate gate contact plugs  70   g   1  adjacent to the second dummy gate contact plug  70   d   2  (i.e., right side of  FIG. 2B ) may also be referred to as a “third intermediate gate contact plug.” 
     In an example embodiment, a length of the upper gate flat dummy region GFd 1  (in  FIGS. 1C and 2A ) of the upper gate flat region GFa (in  FIGS. 1C and 2A ) in the first horizontal direction X may be greater than a length of the intermediate gate flat dummy region GFd 2  of the intermediate gate flat regions GFb in the first horizontal direction X. In an example embodiment, a length of the upper gate flat edge region GFe 1  (in  FIGS. 1C and 2A ) of the upper gate flat region GFa (in  FIGS. 1C and 2A ) in the first horizontal direction X may be substantially the same as a length of the upper gate flat dummy region GFd 1  of the intermediate gate flat region GFb in the first horizontal direction X. The intermediate gate flat region GFb may be referred to as a first gate flat region. The upper gate flat region GFa may be referred to as a second gate flat region. 
     The intermediate gate flat pad region GFp 2  may be referred to as a first gate flat pad region, and the intermediate gate flat edge region GFe 2  may be referred to as a first gate flat edge region. The upper gate flat dummy region GFd 1  may be referred to as a first gate flat dummy region. The upper gate flat dummy region GFd 1  (in  FIGS. 1C and 2A ) may be referred to as a second gate flat dummy region, and the upper gate flat edge region GFe 1  (in  FIGS. 1C and 2A ) may be referred to as a second gate flat edge region. 
     In the description below, the insulating horizontal layers  23 I including the lower insulating horizontal layers  23 Ia, the intermediate insulating horizontal layers  23 Ib, and the floating insulating horizontal layers  23 If will be described with reference to  FIG. 3A . 
     Referring to  FIG. 3A , the insulating horizontal layers  23 I may include pad regions formed in a staircase shape in the connection region EA. The floating insulating horizontal layers  23 If may include floating insulating pads IPf raising with a difference of the second length therebetween in the first horizontal direction X. The intermediate insulating horizontal layers  23 Ib may include intermediate insulating pads IPb lowering in order in the first horizontal direction X with a difference of the first height greater than the second height and first lower insulating pads IPc 1  lowering in order with a difference of the second height in the first horizontal direction X. The lower insulating horizontal layers  23 Ia may include second lower insulating pads IPc 2  lowering in order with a difference of the second height in the first horizontal direction X. 
     A region in which the floating insulating pad IPf is formed may be defined as a floating insulating staircase region ISf, a region in which the intermediate insulating pads IPb are formed may be defined as an intermediate insulating staircase region ISb, a region in which the first lower insulating pads IPc 1  are formed may be defined as a first lower insulating staircase region ISc 1 , and a region in which the second lower insulating pads IPc 2  are formed may be defined as a second lower insulating staircase region ISc 2 . The insulating region IA of the stack structure ST′ may include insulating flat regions IFa, IFb, and IFc. The insulating flat regions IFa, IFb, and IFc may include an upper insulating flat region IFa, an intermediate insulating flat region IFb, and a lower insulating flat region IFc, disposed in order in the first horizontal direction X. 
     The upper insulating flat region IFa may be disposed between the floating insulating staircase region ISf and the intermediate insulating staircase region ISb. The upper insulating flat region IFa (in  FIGS. 1C and 3A ) may include an upper insulating flat dummy region IFd 1  (in  FIGS. 1C and 3A ) and an upper insulating flat edge region IFe 1  (in  FIGS. 1C and 3A ). The lower insulating flat region IFc may be disposed between the first lower insulating staircase region ISc 1  and the second lower insulating staircase region ISc 2 . 
     In an example embodiment, a second dummy pattern  24   di  may be disposed between the lower insulating flat region IFc and the first lower insulating staircase region ISc 1 . The second dummy pattern  24   di  may be disposed on the second interlayer insulating layer  20   b . In an example embodiment, the second dummy pattern  24   di  may be formed of an insulating material, e.g., silicon nitride. 
     In an example embodiment, a plurality of the intermediate insulating staircase regions ISb may be disposed. In an example embodiment, a plurality of the intermediate insulating flat regions IFb may be disposed. One of the plurality of intermediate insulating flat regions IFb may be disposed between intermediate insulating staircase regions adjacent to each other among a plurality of the intermediate insulating staircase region ISb. Accordingly, one or a plurality of the intermediate insulating flat regions IFb may be disposed. 
     Peripheral contact plugs  71  penetrating through the first, second, and third upper insulating layers  33 ,  53 , and  65 , the stack structure ST′, and the gap-fill insulating layer  13 , extending downwardly, and electrically connected to the peripheral contact pads  8 P may be disposed. Gate connection wirings  74   g   1  may be disposed on the peripheral contact plugs  71 . The upper flat region FAa may include the upper gate flat region GFa and the upper insulating flat region IFa adjacent to each other in the second horizontal direction Y. One or a plurality of the intermediate flat regions Fab may include one or a plurality of the intermediate gate flat regions GFb, and one or the plurality of the intermediate insulating flat regions IFb, adjacent to each other in the second horizontal direction Y. The lower flat region FAc may include the lower gate flat region GFc and the lower insulating flat region IFc adjacent to each other in the second horizontal direction Y. 
     One or a plurality of the intermediate gate flat regions GFb may be referred to as a first flat region, the lower flat region FAc may be referred to as a second flat region, and the upper flat region FAa may be referred to as a third flat region. The gate contact plugs  70   g   1 ,  70   g   2 ,  70   d   1  and  70   d   2  (in  FIG. 2B ) may be disposed on the gate region GA of the stack structure ST′, and the peripheral contact plugs  71  may penetrate through the insulating region IA of the stack structure ST′. 
     In the description below, the intermediate insulating flat region IFb will be described with reference to  FIGS. 1D and 3B . 
     Referring to  FIGS. 1D and 3B , each of the intermediate insulating pads IPb may have the first length La in the first horizontal direction X. The intermediate insulating flat region IFb may include an intermediate insulating flat pad region IFp 2 , an intermediate insulating flat edge region IFe 2 , and an insulating flat dummy region IFd 2  disposed between the intermediate insulating flat pad region IFp 2  and the intermediate insulating flat edge region IFe 2 . The intermediate insulating flat pad region IFp 2 , the insulating flat dummy region IFd 2 , and the intermediate insulating flat edge region IFe 2  may be disposed in order in the first horizontal direction X. 
     The intermediate insulating flat pad region IFp 2  may have the second length Lp in the first horizontal direction X similarly to the intermediate gate flat pad region GFp 2  (in  FIGS. 1D and 2B ). The intermediate insulating flat edge region IFe 2  may have the third length Lc in the first horizontal direction X similarly to the intermediate gate flat edge region GFe 2  (in  FIGS. 1D and 2B ). The insulating flat dummy region IFd 2  may have the fourth length Ld in the first horizontal direction X similarly to the intermediate gate flat dummy region GFd 2  (in  FIGS. 1D and 2B ). 
     Similarly to the intermediate gate flat region GFb (in  FIGS. 1D and 2B ), the second length Lp of the intermediate insulating flat pad region IFp 2  may be the same as or greater than the third length Lc of the intermediate insulating flat dummy region IFd 2 . The fourth length Ld may be greater than each of the second length Lp and the third length Lc. The fourth length Ld may be the same as or greater than a sum of the second length Lp and the third length Lc. 
     In an example embodiment, a length of the upper insulating flat dummy region IFd 1  (in  FIGS. 1C and 3A ) of the upper insulating flat region IFa (in  FIGS. 1C and 3A ) in the first horizontal direction X may be greater than a length of the insulating flat dummy region IFd 2  of the intermediate insulating flat region IFb in the first horizontal direction X. 
     In an example embodiment, a length of the upper insulating flat edge region IFe 1  of the upper insulating flat region IFa (in  FIGS. 1C and 3A ) in the first horizontal direction X may be substantially the same as a length of the intermediate insulating flat edge region IFd 1  of the intermediate insulating flat region IFb in the first horizontal direction X. 
     Each of the insulating horizontal layers  23 I may be formed of a first insulating material layer  24   a . Each of the intermediate insulating flat pad region IFp 2 , the intermediate insulating flat edge region IFe 2 , and the intermediate insulating pads IPb may include the first insulating material layer  24   a  and a second insulating material layer  24   b  disposed on the first insulating material layer  24   a . The second insulating material layer  24   b  may have a thickness less than a thickness of the first insulating material layer  24   a . The first insulating material layer  24   a  may be formed of a first silicon nitride, and the second insulating material layer  24   b  may be formed of a second silicon nitride which may be etched at a speed higher than that of etching the first silicon nitride. 
     In an example embodiment, the insulating flat dummy region IFd 2  may be formed of a material different from materials of the first and second insulating material layers  24   a  and  24   b , e.g., silicon oxide. The insulating flat dummy region IFd 2  may be formed of a material the same as a material of the intermediate gate flat dummy region GFd 2  (in  FIG. 2B ). The insulating flat dummy region IFd 2  may separate the first insulating material layer of the intermediate insulating flat pad region IFp 2  from the second insulating material layer of the insulating flat dummy region IFd 2  such that the first insulating material layer may be spaced apart from the second insulating material layer. 
     In an example embodiment, each of the lower gate flat region GFc (in  FIGS. 1B and 2A ) and the lower insulating flat region IFc (in  FIGS. 1B and 3A ) may have a length greater than the first length La of each of the intermediate gate pads GPb in the first horizontal direction X. In an example embodiment, each of the lower gate flat region GFc (in  FIGS. 1B and 2A ) and the lower insulating flat region IFc (in  FIGS. 1B and 2A ) may have a length greater than the third length Lc of each of the intermediate insulating flat edge region IFe 2  and the intermediate gate flat edge region GFe 2  (in  FIGS. 1B and 2A ) in the first horizontal direction X. In an example embodiment, each of the lower gate flat region GFc (in  FIGS. 1B and 2A ) and the lower insulating flat region IFc (in  FIGS. 1B and 3A ) may have a length greater than the second length Lp of each of the intermediate insulating flat pad region IFp 2  and the intermediate gate flat pad region GFp 2  (in  FIGS. 1B and 2A ) in the first horizontal direction X. 
     A cross-sectional structure of the semiconductor device including the stack structure ST′ in the connection region EA will be described with reference to  FIGS. 4A to 5B .  FIG. 4A  is a cross-sectional diagram along line in  FIG. 1D ,  FIG. 4B  is an enlarged diagram of portion “E” in  FIG. 4A ,  FIG. 5A  is a cross-sectional diagram along line IV-IV′ in  FIG. 1D , and  FIG. 5B  is an enlarged diagram of portion “F” in  FIG. 5A . 
     Referring to  FIGS. 1D, 4A, and 5B , block separation structures  62 B may include first to third block separation structures  62 B 1 ,  62 B 2 , and  62 B 3 . An upper surface of the stack structure ST′ may be planar between the first and second block separation structures  62 B 1  and  62 B 2 . The insulating region IA may be disposed between the first and second block separation structures  62 B 1  and  62 B 2 , and may be spaced apart from the first and second block separation structures  62 B 1  and  62 B 2 . The stack structure ST′ may be configured to have a staircase structure lowering in the second horizontal direction Y between the second and third block separation structures  62 B 2  and  62 B 3 . For example, the intermediate gate pads GPb (in  FIG. 2A ) may be lowered in the first horizontal direction X with a difference of the first height therebetween, and may be lowered in the second horizontal direction Y with a difference of the second height therebetween, smaller than the first height. 
     The second auxiliary separation structures  62 S 2  may penetrate through the stack structure ST′ disposed between the second and third block separation structures  62 B 2  and  62 B 3 . 
     The block separation structures  62 B, the second auxiliary separation structures  62 S 2 , and the first auxiliary separation structures  62 S 1  (in  FIGS. 1A and 1B ) may have the same cross-sectional structure. The block separation structures  62 B, the second auxiliary separation structures  62 S 2 , and the first auxiliary separation structures  62 S 1  (in  FIGS. 1A and 1B ) may penetrate through the second upper insulating layer  53 , the first upper insulating layer  33 , and the stack structure ST′ in order. 
     The cross-sectional structure in  FIG. 5B , obtained by cutting out the intermediate insulating flat pad region IFp 2  and the intermediate gate flat pad region GFp 2  in the second horizontal direction Y, will be described. 
     The intermediate insulating flat pad region IFp 2  may include the first insulating material layer  24   a  and the second insulating material layer  24   b  on the first insulating material layer  24   a  as in the example embodiment described with reference to  FIGS. 1D and 3B . 
     In the region in which the intermediate insulating flat pad region IFp 2  is disposed, the intermediate gate horizontal layer of the intermediate gate horizontal layers  23 Gb, adjacent to the intermediate insulating flat pad region IFp 2 , may further include a gate extension portion  25  extending to an upper surface of the first insulating material layer  24   a  included in the intermediate insulating flat pad region IFp 2  and in contact with the second insulating material layer  24   b  of the intermediate insulating flat pad region IFp 2 . The gate extension portion  25  may be formed of a conductive material. 
     The memory vertical structure  36  (in  FIGS. 2A and 3A ) in the memory cell array region MA will be described with reference to  FIG. 6 .  FIG. 6  is a cross-sectional structure taken in the second horizontal direction Y with reference to the insulating separation pattern  34  (in  FIG. 1B ) in the memory cell array region MA. 
     Referring to  FIG. 6 , the insulating separation pattern  34  may penetrate through the first upper insulating layer  33 , may extend downwardly, and may penetrate through the gate horizontal layers  23 G. The memory vertical structure  36  may include a core region  48 , a pad pattern  50  on the core region  48 , a channel layer  46  covering a side surface and a bottom surface of the core region  48  and in contact with the pad pattern  50 , and a dielectric structure  38  enclosing an external side surface of the channel layer  46 . 
     The channel layer  46  may be formed of a semiconductor material. The channel layer  46  may be formed of, e.g., polysilicon. The pad pattern  50  may be formed of, e.g., doped polysilicon, polysilicon having N-type conductivity, for example. The pad pattern  50  may be in contact with the contact plug  90 . The core region  48  may include an insulating material, or an insulating material having a void formed therein. 
     The dielectric structure  38  may include a first dielectric layer  40 , a second dielectric layer  44 , and a data storage material layer  42  disposed between the first dielectric layer  40  and the second dielectric layer  44 . The first dielectric layer  40  may be disposed between the data storage material layer  42  and the stack structure ST′, and the second dielectric layer  44  may be disposed between the data storage material layer  42  and the channel layer  46 . 
     In an example embodiment, the data storage material layer  42  may be configured as an electric charge trapping layer, e.g., silicon nitride. The data storage material layer  42  may include regions which may store data in a semiconductor device, e.g., a vertical-type NAND flash memory device. 
     In an example embodiment, at least a lowermost gate layer of the lower gate horizontal layers  23 Ga may be a gate layer of an erase transistor used for an erase operation of a vertical-type NAND flash memory device using a gate induced drain leakage (GIDL) phenomenon. A gate layer of the lower gate horizontal layers  23 Ga, disposed on the erase transistor gate layer used for an erase operation, may be a ground select gate layer of a ground select transistor. 
     In an example embodiment, a portion of the intermediate gate horizontal layers  23 Gb may be word lines of a vertical-type NAND flash memory device included in memory cells. 
     In an example embodiment, at least an uppermost gate layer of the upper gate horizontal layers  23 Gc may be a gate layer of an erase transistor used for an erase operation of a vertical-type NAND flash memory device using a gate induced drain leakage (GIDL) phenomenon. 
     In an example embodiment, one or a plurality of the gate layers of the upper gate horizontal layers  23 Gc, disposed in a lower portion of a gate layer of the erase transistor, may be gate layers of a string select transistor of the vertical-type NAND flash memory device. 
     In an example embodiment, each of the gate horizontal layers  23 G may include a first layer  23 G 1  and a second layer  23 G 2 . The first layer  23 G 1  may be interposed between the second layer  23 G 2  and the memory vertical structure  36  and may cover an upper surface and a lower surface of the second layer  23 G 2 . 
     In an example embodiment, the first layer  23 G 1  and the second layer  23 G 2  may be formed of different materials. For example, the second layer  23 G 2  may be formed of a conductive material, such as a doped silicon, a metal nitride (e.g., TiN, WN, or the like), a metal-semiconductor compound (e.g., TiSi, WSi, or the like), or a metal (e.g., W, or the like), and the first layer  23 G 1  may be formed of an insulating material. The first layer  23 G 1  may be formed of a high-k dielectric, e.g., aluminum oxide, or the like. In another example embodiment, the first layer  23 G 1  may be formed of a metal nitride (e.g., TiN, WN, or the like), and the second layer  23 G 2  may be formed of a metal (e.g., W, or the like). In yet another example embodiment, each of the gate horizontal layers  23 G may be formed of a single conductive material, such as a doped silicon, a metal nitride (e.g., TiN, WN, or the like), a metal-semiconductor compound (e.g., TiSi, WSi, or the like), or a metal (e.g., W, or the like). 
     In an example embodiment, the dielectric structure  38  may include the data storage material layer  42  including regions which may store data of a vertical-type NAND flash memory device, but an example embodiment thereof is not limited thereto. For example, the dielectric structure  38  may include a data storage material layer which may store data of a resistance change memory (ReRAM) device or a data storage material layer which may store data of a PRAM device, instead of the data storage material layer  42 . 
     Referring back to  FIG. 3B , as described above, the intermediate insulating flat dummy region IFd 2  may not include the first insulating material layer  24   a  and the second insulating material layer  24   b . The intermediate insulating flat dummy region IFd 2  (in  FIG. 3B ) may be, however, modified to form an intermediate insulating flat dummy region IFd 2 ′ as in  FIG. 7A .  FIG. 7A  is an enlarged diagram illustrating a modified example of the intermediate insulating flat dummy region IFd 2  illustrated in  FIG. 3B . 
     In the modified example embodiment, referring to  FIG. 7A , the intermediate insulating flat dummy region IFd 2  (in  FIG. 3B ) may be replaced with the intermediate insulating flat dummy region IFd 2 ′ illustrated in  FIG. 7A . The intermediate insulating flat dummy region IFd 2 ′ may have a reduced thickness and may extend from the first insulating material layer  24   a  of the intermediate insulating flat plug region IFp 2  and the intermediate insulating flat edge region IFe 2 . Accordingly, the intermediate insulating flat dummy region IFd 2 ′ may include a first insulating material layer  24   a ′, e.g., that is continuous and integral with the first insulating material layer  24   a , that has a reduced thickness relative to the first insulating material layer  24   a , e.g., along the vertical direction Z. 
     A minimum thickness of the first insulating material layer  24   a ′ of the intermediate insulating flat dummy region IFd 2 ′ may be less than a maximum thickness of the intermediate insulating flat pad region IFp 2  and a maximum thickness of the first insulating material layer  24   a  of the intermediate insulating flat edge region IFe 2 , e.g., along the vertical direction Z. The intermediate insulating flat dummy region IFd 2 ′ may not include the second insulating material layer  24   b.    
     Referring back to  FIG. 2B , as described above, the intermediate gate flat dummy region GFd 2  may not include a conductive material and may be formed of an insulating material. The intermediate gate flat dummy region GFd 2  (in  FIG. 2B ) may be modified to an intermediate gate flat dummy region GFd 2 ′ as in  FIG. 7B .  FIG. 7B  is an enlarged diagram illustrating a portion illustrated in  FIG. 2B , illustrating a modified example of the intermediate gate flat dummy region GFd 2  (in  FIG. 2B ). 
     In the modified example embodiment, referring to  FIG. 7B , the intermediate gate flat dummy region GFd 2  (in  FIG. 2B ) may be replaced with the intermediate gate flat dummy region GFd 2 ′ illustrated in  FIG. 7B . 
     As illustrated in  FIG. 7B , the intermediate gate flat pad region GFp 2  may include a first conductive layer, and the intermediate gate flat edge region GFe 2  may include a second conductive layer. The intermediate gate flat dummy region GFd 2 ′ may include a third conductive layer having a reduced thickness and extending from the first conductive layer of the intermediate gate flat pad region GFp 2  and the second conductive layer of the intermediate gate flat edge region GFe 2 . The first conductive layer, the third conductive layer, and the second conductive layer may extend consecutively without a boundary surface therebetween, e.g., may be integral with each other as a single and uniform layer. The first conductive layer of the gate flat pad region GFp 2  and the second conductive layer of the gate flat edge region GFe 2  may have the same maximum thickness. A maximum thickness of each of the first and second conductive layers may be greater than a minimum thickness of the third conductive layer of the intermediate gate flat dummy region GFd 2 ′, e.g., along the vertical direction Z. 
     Referring to  FIG. 1A , each of the second auxiliary separation structures  62 S 2  may have a line shape consecutively connected to each other in the first horizontal direction X, but an example embodiment thereof is not limited thereto. Each of the second auxiliary separation structures  62 S 2  may be modified to form second auxiliary separation structures  62 S 2 ′ illustrated in  FIG. 8 .  FIG. 8  is a plan diagram illustrating a modified example of the second auxiliary separation structures  62 S 2  illustrated in  FIG. 1A . 
     Referring to  FIG. 8A , the second auxiliary separation structures  62 S 2  (in  FIG. 1A ) may be replaced with the second auxiliary separation structures  62 S 2 ′ illustrated in  FIG. 8 . Each of the second auxiliary separation structures  62 S 2 ′ may include a plurality of line patterns spaced apart from each other in the first horizontal direction X. 
     In the description below, a modified example of a semiconductor device will be described with reference to  FIGS. 9 and 10A-10B .  FIG. 9  is a plan diagram illustrating a modified example of a semiconductor device according to an example embodiment,  FIG. 10A  is a cross-sectional diagram along line Ia-Ia′ in  FIG. 9 , and  FIG. 10B  is a cross-sectional diagram along line IIa-IIa′ in  FIG. 9 . Overlapping descriptions will not be provided, and a modified portion will mainly be described. 
     Referring to  FIGS. 9, 10A, and 10B , substantially the same memory cell array region MA and the same connection region EA, described with reference to  FIGS. 1A to 5B , may be provided. A stack structure ST″ disposed in the same memory cell array region MA and extending into the connection region EA may be disposed. The stack structure ST″ may include substantially the same gate region GA and the same insulating region IA described with reference to  FIGS. 1A to 5B . The plurality of separation structures  62 B,  62 S 1 , and  62 S 2 , substantially the same as in the example embodiment described with reference to  FIGS. 1A to 5B  may be disposed. The second auxiliary separation structures  62 S 2  of the plurality of separation structures  62 B,  62 S 1 , and  62 S 2  disposed in the connection region EA may be configured to have a line shape extending in the first horizontal direction X as in  FIGS. 1A and 1B , or bar shapes spaced apart from each other in the first horizontal direction X as in  FIG. 8 . 
     The lower structure  3  described with reference to  FIGS. 1A to 5B  may be disposed. The lower stack structure ST 1 ′ having a shape substantially the same as in the aforementioned example embodiment may be disposed on the lower structure  3 . For example, the lower stack structure ST 1 ′ may include a lower flat region FAc′ corresponding to the lower flat region FAc (in  FIG. 1B ), and the lower flat region FAc′ may include a lower gate flat region GFc′ and a lower insulating flat region IFc′ corresponding to the lower gate flat region GFc (in  FIG. 1B ) and the lower insulating flat region IFc (in  FIG. 1B ), respectively. The lower stack structure ST 1 ′ may include the second lower gate staircase region GSc 2  in which the second lower gate pads GPc 2  is formed, and the second lower insulating staircase region ISc 2  in which the second lower insulating pads IPc 2  is formed. 
     A first upper stack structure ST 2   a  having a shape substantially the same as that of the upper stack structure ST 2 ′ described with reference to  FIGS. 1A to 3B  may be disposed on the lower stack structure ST 1 ′. The first upper insulating layer  33 , the same as in the aforementioned example embodiment, may be disposed on the lower stack structure ST 1 ′ and the first upper stack structure ST 2   a.    
     The first upper stack structure ST 2   a  may include one or the plurality of intermediate flat regions Fab (in  FIG. 1B ) described in the aforementioned example embodiment, one or the plurality of first intermediate flat regions FAba corresponding to the upper flat region FAa (in  FIG. 1B ), and a first upper flat region FAaa. The one or the plurality of first intermediate flat regions FAba may include the one or the plurality of the intermediate gate flat regions GFb (in  FIG. 1B ), and the one or the plurality of intermediate gate flat regions GFba (in  FIG. 1B ) corresponding to one or the plurality of single intermediate insulating flat regions IFb (in  FIG. 1B ). The first upper flat regions FAaa may include a first upper gate flat region GFaa and a first upper insulating flat region IFaa corresponding to the upper gate flat region GFa (in  FIG. 1B ) and the upper insulating flat region IFa (in  FIG. 1B ), respectively. 
     A second upper stack structure ST 2   b  having a shape substantially the same as that of the upper stack structure ST 2 ′ described with reference to  FIGS. 1A to 3B  may be disposed on the first upper insulating layer  33 . An additional upper insulating layer  133  may be disposed on the first upper insulating layer  33  and the second upper stack structure ST 2   b.    
     The second upper stack structure ST 2   b  may include the one or the plurality of intermediate flat regions Fab (in  FIG. 1B ), one or a plurality of second intermediate flat regions FAbb corresponding to the upper flat region FAa (in  FIG. 1B ), and a second upper flat region FAab. The one or a plurality of second intermediate flat regions FAbb may include the one or the plurality of intermediate gate flat regions GFb (in  FIG. 1B ) described in the aforementioned example embodiment, one or a plurality of second intermediate gate flat regions GFbb corresponding to the one or the plurality of intermediate insulating flat regions IFb (in  FIG. 1B ), and one or a plurality of second intermediate insulating flat regions IFbb. The second upper flat regions FAab may include a second upper gate flat region GFab and a second upper insulating flat region IFab corresponding to the upper gate flat region GFa (in  FIG. 1B ) and the upper insulating flat regions IFa (in  FIG. 1B ), respectively. 
     In the cross-sectional structure illustrated in  FIG. 10A , each of the first and second upper stack structures ST 2   a  and ST 2   b  may include the intermediate gate staircase region GSb on which the intermediate gate pads GPb are formed, the floating gate staircase region GSf on which the floating gate pads GPf are formed, and the upper gate staircase region GSa on which the upper gate pads GPa are formed. 
     In the cross-sectional structure illustrated in  FIG. 10B , each of the first and second upper stack structures ST 2   a  and ST 2   b  may include the intermediate insulating staircase region ISb in which the intermediate insulating pads IPb are formed, and the floating insulating staircase region ISf in which the floating insulating pad IPf is formed. In the cross-sectional structure illustrated in  FIG. 10B , the first upper stack structure ST 2   a  may further include an upper insulating staircase region Isa in which the upper insulating pads IPa, each having a cross-sectional shape substantially the same as that of the upper gate staircase region GSa including the upper gate pads GPa, is formed, and the second upper stack structure ST 2   b  may further include the upper gate staircase region GSa in which the upper gate pads GPa are disposed as in  FIG. 3A . 
     The stack structure ST″ may include the lower stack structure ST 1 ′, the first upper stack structure ST 2   a , and the second upper stack structure ST 2   b.    
     A memory vertical structure  136  penetrating through the additional upper insulating layer  133 , the second upper stack structure ST 2   b , the first upper stack structure ST 2   a , and the first stack region ST 1  in order may be disposed. The memory vertical structure  136  may include the elements substantially the same as the elements included in the memory vertical structure  36  described with reference to  FIG. 6 . 
     The second and third upper insulating layers  53  and  65  described in the aforementioned example embodiment may be disposed on the additional upper insulating layer  133 . Also, peripheral contact plugs  171  and the gate connection wirings  174   g   1 , corresponding to the peripheral contact plugs  71  and the gate connection wirings  74   g   1 , respectively, may be disposed. 
     In the description below, a method of forming a semiconductor device will be described with reference to  FIGS. 11A to 12C .  FIGS. 11A and 12A  are cross-sectional diagrams along line I-I′ in  FIG. 1B ,  FIGS. 11B and 12B  are cross-sectional diagrams along line II-IF in  FIG. 1B , and  FIGS. 11C and 12C  are cross-sectional diagrams along line in  FIG. 1D . 
     In the description of the method of forming the semiconductor device described with reference to  FIGS. 11A to 12C , the description of the structure of the semiconductor device described with reference to  FIGS. 1A to 5B  will not be provided, and the method of forming the semiconductor device described with reference to  FIGS. 1A to 5B  will be described. 
     Referring to  FIGS. 1B, 1D, and 11A to 11C , the integrated circuit region  7  may be formed on the lower substrate  5 . The lower substrate  5  may be configured as a semiconductor substrate. For example, the lower substrate  5  may be configured as single crystalline silicon substrate. The integrated circuit region  7  may include the circuit wirings  8  and the lower insulating layer  9  covering the circuit wirings  8 . The circuit wirings  8  may include the peripheral contact pads  8 P. The upper substrate  12  may be disposed on the integrated circuit region  7 . The upper substrate  12  may be configured as a polysilicon substrate. The gap-fill insulating layer  13  penetrating through the upper substrate  12  may be disposed. 
     A preliminary stack structure ST may be disposed on the upper substrate  12 . The preliminary stack structure ST may be disposed in the memory cell array region MA and the connection region EA on the upper substrate  12 . Forming of the preliminary stack structure ST may include forming a preliminary lower stack structure ST 1  on the upper substrate  12 , and forming a preliminary upper stack structure ST 2  on the preliminary lower stack structure ST 1 . 
     Forming the preliminary lower stack structure ST 1  may include forming first interlayer insulating layers  20   a  and lower horizontal layers  22 L alternately stacked, patterning the first interlayer insulating layers  20   a  and the lower horizontal layers  22 L, forming lower pad regions of the lower horizontal layers  22 L, and forming a second interlayer insulating layer  20   b  covering the lower horizontal layers  22 L. The preliminary upper stack structure ST 2  may be disposed on the preliminary lower stack structure ST 1 . 
     Forming the preliminary upper stack structure ST 2  may include forming third interlayer insulating layers  20   c  and horizontal layers  22 M,  22 U, and  23 F alternately stacked, patterning the third interlayer insulating layers  20   c  and the horizontal layers  22 M,  22 U, and  23 F, forming pad regions Pa, Pb, P 1 , and P 2  arranged in a staircase structure in the connection region EA, and forming pad capping layers  23 R on the pad regions Pa, Pb, P 1 , and P 2 . The stack structure ST may be formed to include the flat regions FAa, FAb, and Fac, each having a length greater than a length of each of the pad regions Pa, Pb, P 1 , and P 2  and configured to be planar in the first horizontal direction X. 
     In an example embodiment, the pad capping layers  23 R may not be disposed on an uppermost horizontal layer of the horizontal layers  22 M,  22 U, and  23 F. In another example embodiment, the pad capping layers  23 R may be disposed on an uppermost horizontal layer of the horizontal layers  22 M,  22 U, and  23 F. 
     A photoresist pattern  30  may be formed. The photoresist pattern  30  may have an opening for exposing a portion of each of the flat regions FAa, FAb, and FAc. The photoresist pattern  30  may expose pad regions of the lower horizontal layers  22 L. 
     Referring to  FIGS. 1B, 1D, and 12A to 12C , the pad capping layers  23 R which are not covered by the photoresist pattern  30  may be etched using the photoresist pattern  30 . For example, only the pad capping layers  23 R may be selectively etched. In another example, while the pad capping layers  23 R are etched, the preliminary horizontal layers  22  in contact with the pad capping layers  23 R may be partially etched. In yet another example, while the pad capping layers  23 R are etched, the preliminary horizontal layers  22  in contact with the pad capping layers  23 R may be entirely etched. In still another example, while the pad capping layers  23 R are etched, the preliminary horizontal layers  22  in contact with the pad capping layers  23 R may be etched, and one of the interlayer insulating layers  20 , exposed while the preliminary horizontal layers  22  are etched, may be etched. 
     The photoresist pattern  30  may be removed. The first upper insulating layer  33  may be formed on the stack structure ST. 
     The memory vertical structure  36  penetrating through the first upper insulating layer  33  and the stack structure ST may be formed. The memory vertical structure  36  may be formed in the memory cell array region MA. A second upper insulating layer  53  may be disposed on the first upper insulating layer  33 . 
     Separation trenches  61 B and  61 C penetrating through the second upper insulating layer  53 , the first upper insulating layer  33 , and the stack structure ST may be formed. The separation trenches  61 B and  61 C may be disposed in positions corresponding to positions of the separation structures  62 B,  62 S 1 , and  62 S 2  illustrated in  FIGS. 1A to 5B . 
     A portion of the preliminary horizontal layers  22  and a portion of the pad capping layers  23 R may be replaced with the gate horizontal layers  23 G. Accordingly, preliminary horizontal layers of the preliminary horizontal layers  22  which are not replaced with the gate horizontal layers  23 G, and the pad capping layers may be defined as insulating horizontal layers  23 I. Accordingly, horizontal layers including the insulating horizontal layers  23 I and the gate horizontal layers  23 G may be disposed. 
     In an example embodiment, replacing a portion of the preliminary horizontal layers  22  and a portion of the pad capping layers  23 R with the gate horizontal layers  23 G may include forming empty spaces by partially etching the preliminary horizontal layers  22  and the pad capping layers  23 R exposed through the separation trenches  61 B and  61 S and filling the empty spaces with the gate horizontal layers  23 G. Accordingly, the stack structure ST′ including the horizontal layers  23 G and  23 I and the interlayer insulating layers  20 , described with reference to  FIGS. 1A and 5B  may be formed. 
     In the semiconductor device in the aforementioned example embodiments, the stack structure ST′ may include the plurality of interlayer insulating layers  20  and the plurality of horizontal layers  23 G and  23 I, and the plurality of interlayer insulating layers  20  and the plurality of horizontal layers  23 G and  23 I may be alternately stacked in the memory cell array region MA, and may extend into the connection region EA adjacent to the memory cell array region MA. In the connection region EA, the stack structure ST′ may include a staircase region and a flat region adjacent to the staircase region. The staircase region may include pads lowering in the first horizontal direction, each of the pads may have a first length in the first horizontal direction, and the flat region may include a flat pad region having a second length greater than the first length in the first horizontal direction, a flat edge region having a third length greater than the first length in the first horizontal direction, and a flat dummy region disposed between the flat pad region and the flat edge region. A fourth length of the flat dummy region in the first horizontal direction may be greater than each of the second length and the third length. 
     The staircase region may be configured as the intermediate gate staircase region GSb illustrated in  FIGS. 2A and 2B  or the intermediate insulating staircase region ISb illustrated in  FIGS. 3A and 3B , and the flat region may be configured as the intermediate gate flat region GFb illustrated in  FIGS. 2A and 2B  or the intermediate insulating flat region IFb illustrated in  FIGS. 3A and 3B . The flat pad region may be configured as the gate flat pad region GFp 2  illustrated in  FIG. 2B  or the insulating flat pad region IFp 2  illustrated in  FIG. 3B . The flat dummy region may be configured as the gate flat dummy region GFd 2  illustrated in  FIG. 2B  or the insulating flat dummy region IFd 2  illustrated in  FIG. 3B . By providing the stack structure ST′ including the flat regions as described above, integration density of the semiconductor device may increase. 
     According to the aforementioned example embodiments, by providing the stack structure including a gate region and an insulating region on the lower structure including a peripheral circuit region, integration density of the semiconductor device may improve. Also, by providing the stack structure including the flat region and the contact plugs crossing the flat region and penetrating through the stack structure on the lower structure including the peripheral circuit region, integration density of the semiconductor device may improve. 
     By way of summation and review, as the number of the gate electrodes stacked in a direction perpendicular to a surface of a semiconductor substrate increases, the difficulty of electrically connecting the gate electrodes to a peripheral circuit increases and unexpected defects may occur. In contrast, example embodiments provide a semiconductor device which may improve integration density. 
     That is, in order to implement high integration density, a semiconductor device, according to example embodiments, includes a stack structure where a portion thereof above a peripheral circuit is configured as an insulating region, such that peripheral contact plugs penetrate the insulating region of the stack structure. In this case, mold layers used for forming word lines remain in the insulating region to prevent the insulating region from decreasing while forming the word lines, a method of patterning a portion of the mole layers formed in the insulating region may be suggested. 
     Example embodiments have been disclosed herein, and although specific terms are employed, they are used and are to be interpreted in a generic and descriptive sense only and not for purpose of limitation. In some instances, as would be apparent to one of ordinary skill in the art as of the filing of the present application, features, characteristics, and/or elements described in connection with a particular embodiment may be used singly or in combination with features, characteristics, and/or elements described in connection with other embodiments unless otherwise specifically indicated. Accordingly, it will be understood by those of skill in the art that various changes in form and details may be made without departing from the spirit and scope of the present invention as set forth in the following claims.