Patent Publication Number: US-2022223711-A1

Title: Semiconductor devices including separation structure

Description:
CROSS-REFERENCE TO THE RELATED APPLICATION 
     This non-provisional patent application claims priority, under 35 U.S.C. § 119, from Korean Patent Application No. 10-2021-0002272, filed on Jan. 8, 2021, in the Korean Intellectual Property Office, the inventive concepts of which is incorporated herein by reference in its entirety. 
     BACKGROUND 
     1. Field 
     Some example embodiments of the inventive concepts relate to semiconductor devices including a separation structure between source/drain regions, and formation methods thereof. 
     2. Description of the Related Art 
     In accordance with high integration of a semiconductor device, electrically separating a plurality of elements becomes more difficult. For example, the spacing among a plurality of sources/drains is gradually reduced. Such a reduction in the spacing among the plurality of sources/drains may cause an increase in leakage current. 
     SUMMARY 
     Some example embodiments of the inventive concepts provide semiconductor devices having excellent electrical characteristics while being advantageous in terms of mass production efficiency, and formation methods thereof. 
     A semiconductor device according to some example embodiments of the inventive concepts includes a plurality of active regions on a substrate. A gate electrode intersects the plurality of active regions. A plurality of source/drain regions are on the plurality of active regions such that the plurality of source/drain regions are adjacent to opposite sides of the gate electrode and the gate electrode is between the plurality of source/drain regions. A separation structure is between adjacent source/drain regions of the plurality of source/drain regions. The separation structure includes an insulating pattern and a spacer layer. The insulating pattern includes first and second side surfaces that are opposite side surfaces of the insulating pattern and are adjacent to separate, respective source/drain regions of the adjacent source/drain regions. The spacer layer is disposed on the first and second side surfaces. An uppermost end of the insulating pattern is farther from a lower surface of the substrate than a first upper surface of the spacer layer that is adjacent to the first and second side surfaces. 
     A semiconductor device according to some example embodiments of the inventive concepts includes an element isolation layer defining a plurality of active regions on a substrate. A gate electrode intersects the plurality of active regions while extending on the element isolation layer. A plurality of source/drain regions are on the plurality of active regions, such that the plurality of source/drain regions are adjacent to opposite sides of the gate electrode and the gate electrode is between the plurality of source/drain regions. A separation structure is on the element isolation layer and between adjacent source/drain regions of the plurality of source/drain regions. The separation structure includes an insulating pattern and a spacer layer. The insulating pattern includes first and second side surfaces that are opposite side surfaces of the insulating pattern and are adjacent to separate, respective source/drain regions of the adjacent source/drain regions. The spacer layer is disposed on the first side surface, the second side surface and the third side surface. An uppermost end of the insulating pattern is farther from a lower surface of the substrate than a first upper surface of the spacer layer that is adjacent to the first and second side surfaces. The uppermost end of the insulating pattern is nearer to the lower surface of the substrate than a second upper surface of the spacer layer that is adjacent to the third side surface. 
     A semiconductor device according to some example embodiments of the inventive concepts includes an element isolation layer defining a plurality of active regions on a substrate. A plurality of gate electrodes intersect the plurality of active regions while extending on the element isolation layer. A plurality of source/drain regions are on the plurality of active regions adjacent to opposite sides of each of the gate electrodes. A separation structure is on the element isolation layer between adjacent source/drain regions of the plurality of source/drain regions and between adjacent gate electrodes of the plurality of gate electrodes. The separation structure includes an insulating pattern and a spacer layer. The insulating pattern includes first and second side surfaces that are opposite side surfaces of the insulating pattern and are adjacent to separate, respective source/drain regions of the adjacent source/drain regions, and a third side surface adjacent to the gate electrode. The spacer layer is disposed on the first side surface, the second side surface, the third side surface and the fourth side surface. An uppermost end of the insulating pattern is farther from a lower surface of the substrate than a first upper surface of the spacer layer that is adjacent to the first and second side surfaces. The uppermost end of the insulating pattern is nearer to the lower surface of the substrate than a second upper surface of the spacer layer that is adjacent to the third and fourth side surfaces. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIGS. 1, 2, 3, and 4  are cross-sectional views explaining semiconductor devices according to some example embodiments of the inventive concepts. 
         FIG. 5  is a layout of semiconductor devices according to some example embodiments of the inventive concepts. 
         FIGS. 6, 7, 8, 9, 10, and 11  are cross-sectional views explaining semiconductor devices according to some example embodiments of the inventive concepts. 
         FIGS. 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, and 32  are cross-sectional views explaining formation methods of semiconductor devices according to some example embodiments of the inventive concepts. 
     
    
    
     DETAILED DESCRIPTION 
       FIGS. 1, 2, 3, and 4  are cross-sectional views explaining semiconductor devices according to some example embodiments of the inventive concepts.  FIG. 5  is a layout of semiconductor devices according to some example embodiments of the inventive concepts.  FIG. 1  may be a cross-sectional view taken along line  1 - 1 ′ in  FIG. 5 .  FIG. 2  may be a cross-sectional view taken along line  2 - 2 ′ in  FIG. 5 .  FIG. 3  may be a cross-sectional view taken along line  3 - 3 ′ in  FIG. 5 .  FIG. 4  may be a cross-sectional view taken along line  4 - 4 ′ in  FIG. 5 . In some example embodiments, semiconductor devices according to some example embodiments of the inventive concepts may include a multi-bridge channel transistor such as MBCFET, a fin field effect transistor (FinFET), a nanowire transistor, a vertical transistor, a recess channel transistor, a 3-D transistor, a planar transistor, or a combination thereof. 
     Referring to  FIG. 1 , a semiconductor device according to some example embodiments of the inventive concepts may include a substrate  21 , an element isolation layer  23 , a plurality of active regions F 1  and F 2 , a plurality of separation structures SP, a plurality of source/drain regions  60 , and an interlayer insulating layer  65 . The active regions F 1  and F 2  may be referred to as being “on” the substrate  21 . The active regions may be referred to as being portions of the substrate  21  that are at least partially defined by an element isolation layer  23  and may be referred to as being at least partially “in” the substrate  21 . Each of the plurality of separation structures SP may include a first spacer layer  51 , a second spacer layer  52 , and an insulating pattern  55 . In some example embodiments, the first spacer layer  51  and the second spacer layer  52  may be collectively referred to as a spacer layer  54  on (e.g., in direct contact with) the first and second side surfaces  55 S 1  and  55 S 2 . In some example embodiments, either of the first spacer layer  51  or the second spacer layer  52  may be referred to as a spacer layer on (e.g., indirectly on or in direct contact with) the first and second side surfaces  55 S 1  and  55 S 2 . In some example embodiments, one of the first spacer layer  51  or the second spacer layer  52  may be omitted, and the remainder of the first spacer layer  51  or the second spacer layer  52  may be referred to as a spacer layer  54  on (e.g., indirectly on or in direct contact with) the first and second side surfaces  55 S 1  and  55 S 2 . The insulating pattern  55  may include a first side surface  55 S 1  and a second side surface  55 S 2  which face each other (e.g., are opposite side surfaces of the insulating pattern  55  as shown in at least  FIG. 1 ). The spacer layer (e.g.,  51 ,  52 , and/or  54 ) may be referred to as being adjacent to the first and second side surfaces  55 S 1  and  55 S 2 . Each of the plurality of source/drain regions  60  may include a first layer  61 , a second layer  62 , and a third layer  63 . 
     Referring to  FIG. 2 , semiconductor devices according to some example embodiments of the inventive concepts may include a substrate  21 , a first active region F 1 , a first spacer layer  51 , a plurality of source/drain regions  60 , a plurality of insulating plugs  59 , an interlayer insulating layer  65 , a gate dielectric layer  71 , and a plurality of gate electrodes G 1  to G 3 . The first active region F 1  may include a plurality of active patterns  31  to  35  contacting the source/drain regions  60 . For example, the plurality of active patterns  31  to  35  may include a first active pattern  31 , a second active pattern  32 , a third active pattern  33 , a fourth active pattern  34 , and a fifth active pattern  35 . Each of the plurality of source/drain regions  60  may include a first layer  61 , a second layer  62 , and a third layer  63 . The plurality of gate electrodes G 1  to G 3  may include a first gate electrode G 1 , a second gate electrode G 2 , and a third gate electrode G 3 . 
     Referring to  FIG. 3 , semiconductor devices according to some example embodiments of the inventive concepts may include a substrate  21 , an element isolation layer  23 , a first active region F 1 , a gate dielectric layer  71 , and a first gate electrode G 1 . The first active region F 1  may include a plurality of active patterns  31  to  35 . For example, the plurality of active patterns  31  to  35  may include a first active pattern  31 , a second active pattern  32 , a third active pattern  33 , a fourth active pattern  34 , and a fifth active pattern  35 . 
     Referring to  FIG. 4 , semiconductor devices according to some example embodiments of the inventive concepts may include a substrate  21 , an element isolation layer  23 , a first spacer layer  51 , a second spacer layer  52 , a plurality of insulating patterns  55 , an interlayer insulating layer  65 , a gate dielectric layer  71 , and a plurality of gate electrodes G 1  to G 3 . Each of the plurality of insulating patterns  55  may include a third side surface  55 S 3  and a fourth side surface  55 S 4  facing each other. The plurality of gate electrodes G 1  to G 3  may include a first gate electrode G 1 , a second gate electrode G 2 , and a third gate electrode G 3 . 
     Referring to  FIG. 5 , semiconductor devices according to some example embodiments of the inventive concepts may include a plurality of active regions F 1  to F 6 , a plurality of gate electrodes G 1  to G 3 , and a plurality of separation structures SP. The plurality of active regions F 1  to F 6  may include a first active region F 1 , a second active region F 2 , a third active region F 3 , a fourth active region F 4 , a fifth active region F 5 , and a sixth active region F 6 . The plurality of gate electrodes G 1  to G 3  may include a first gate electrode G 1 , a second gate electrode G 2 , and a third gate electrode G 3 . 
     Again referring to  FIGS. 1 to 5 , the element isolation layer  23  may be provided on the substrate  21 , to define the plurality of active regions F 1  to F 6  on the substrate  21 . The plurality of active regions F 1  to F 6  may be parallel. As shown in  FIGS. 1 to 5 , the plurality of gate electrodes G 1  to G 3  may be provided to extend on the element isolation layer  23  while intersecting the plurality of active regions F 1  to F 6 . As shown in  FIGS. 1 to 5 , the plurality of gate electrodes G 1  to G 3  may be parallel (e.g., extend in parallel to each other). As shown in  FIGS. 1 to 5 , the plurality of gate electrodes G 1  to G 3  may each intersect the plurality of active regions F 1  to F 6 . As shown in  FIGS. 1 to 5 , each of the plurality of gate electrodes G 1  to G 3  may perpendicularly intersect the plurality of active regions F 1  to F 6 . 
     The plurality of source/drain regions  60  may be provided to be disposed on the plurality of active regions F 1  to F 6  adjacent to opposite sides of each of the plurality of gate electrodes G 1  to G 3 . As shown in  FIGS. 1-5 , the plurality of source/drain regions  60  may be adjacent to opposite sides of the gate electrodes G 1  to G 3 , such that each gate electrode G 1 , G 2 , G 3  is between (e.g., horizontally between) adjacent source/drain regions  60  of the plurality of source/drain region  60 . For example, as shown in  FIGS. 1 to 5 , two adjacent source/drain regions  60  may be adjacent to opposite sides of the first gate electrode G 1  such that the first gate electrode G 1  is between the two adjacent source/drain regions  60 . Each of the plurality of active patterns  31  to  35  may contact the plurality of source/drain regions  60 . The gate electrodes G 1  to G 3  may cover upper and side surfaces of the plurality of active patterns  31  to  35 . In some example embodiments, the second active pattern  32 , the third active pattern  33 , the fourth active pattern  34  and the fifth active pattern  35  may be sequentially vertically aligned on the first active pattern  31 . The plurality of gate electrodes G 1  to G 3  may surround upper, lower and side surfaces of each of the second active pattern  32 , the third active pattern  33 , the fourth active pattern  34  and the fifth active pattern  35 , and may cover upper and side surfaces of the first active pattern  31 . 
     The plurality of separation structures SP may be provided to be disposed on the element isolation layer  23  disposed among the plurality of source/drain regions  60  and the plurality of gate electrodes G 1  to G 3 . For example, as shown in  FIGS. 1 to 5 , each separation structure SP may be between adjacent source/drain regions  60  (e.g., between in a first horizontal direction) and/or between adjacent gate electrodes G 1  to G 3  (e.g., between in a second horizontal direction that intersects and/or is perpendicular to the first horizontal direction( ). Each of the plurality of separation structures SP may include the first spacer layer  51 , the second spacer layer  52 , and the insulating pattern  55 . The insulating pattern  55  may include the first side surface  55 S 1  and the second side surface  55 S 2  which face each other (e.g., are first opposite side surfaces of the insulating pattern  55 ). Each of the first side surface  55 S 1  and the second side surface  55 S 2  may be adjacent to a corresponding one of the plurality of source/drain regions  60 . Restated, and as shown in at least  FIG. 1 , the first side surface  55 S 1  and the second side surface  55 S 2  of an insulating pattern  55  of a given separation structure SP, which may be adjacently between two adjacent source/drain regions  60 , may be adjacent to (e.g., directly contacting and/or proximate to) separate, respective source/drain regions  60  of the two adjacent source/drain regions  60 . The insulating pattern  55  may include the third side surface  55 S 3  and the fourth side surface  55 S 4 . Each of the third side surface  55 S 3  and the fourth side surface  55 S 4  may be adjacent to a corresponding one of the plurality of gate electrodes G 1  to G 3 . The third side surface  55 S 3  and the fourth side surface  55 S 4  may face each other and/or may be second opposite side surfaces of the insulating pattern  55  that are adjacent to separate, respective gate electrodes of the adjacent gate electrodes of the gate electrodes G 1  to G 3 . 
     The second spacer layer  52  may be between the first spacer layer  51  and the insulating pattern  55 . The second spacer layer  52  may partially surround the first to fourth side surfaces  55 S 1 ,  55 S 2 ,  55 S 3  and  55 S 4  of the insulating pattern  55  and a bottom (e.g., lower surface  55   b ) of the insulating pattern  55 . Accordingly, it will be understood that the spacer layer  54  may surround (in direct contact with or isolated from direct contact with, a direction perpendicular to the lower surface  21   s  (e.g., a vertical direction) and/or a direction parallel to the lower surface  21   s  (e.g., a horizontal direction)) the lower surface  55   b  of the insulating pattern  55 . It will be understood that the spacer layer  54  (e.g.,  51  and/or  52 ) may be on the first to fourth side surfaces  55 S 1  to  55 S 4 . The spacer layer  54  (e.g., the first and/or second spacer layers  51  and/or  52 ) may be between the insulating pattern  55  and at least one gate electrode. The first spacer layer  51  may be disposed outside the second spacer layer  52 . The first spacer layer  51  may extend between the element isolation layer  23  and the insulating pattern  55 . The second spacer layer  52  may be disposed between the first spacer layer  51  and the insulating pattern  55 . Accordingly, it will be understood that the spacer layer  54  may extend between the element isolation layer  23  and the insulating pattern  55 . 
     An uppermost end  55   u  of the insulating pattern  55  may protrude to a higher level (e.g., may be further from the lower surface  21   s  in the direction perpendicular to the lower surface  21   s ) than a center  60   c  of each of the plurality of source/drain regions  60 , for example as shown in  FIG. 1 . The center  60   c  of each source/drain region  60  may refer to a point or location that is equidistant from an uppermost end  60   u  and a lowermost end  60 L of the source/drain region. As shown in at least  FIG. 1 , the uppermost end  55   u  of the insulating pattern  55  may protrude to a higher level than a portion  60   w  of the source/drain regions  60  having a maximum horizontal width w 1  from among portions of each of the plurality of source/drain regions  60  (e.g., the portion  60   w  of each source/drain region  60  having a maximum horizontal width w 1  of the source/drain region  60  in the direction that is parallel to the lower surface  21   s.  The plurality of source/drain regions  60  may contact (e.g., directly contact) the first and second side surfaces  55 S 1  and  55 S 2 . Restated, where a separation structure SP is between adjacent source/drain regions  60 , the adjacent source/drain regions may directly contact separate, respective surfaces of the first and second side surfaces  55 S 1  and  55 S 2 . Uppermost ends  60   u  of the plurality of source/drain regions  60  may protrude to a higher level than the uppermost end  55   u  of the insulating pattern  55 . 
     As described herein, a “level” of a surface, end, structure, or the like may refer to a distance from the lower surface  21   s  of the substrate  21  in a direction that is perpendicular to the lower surface  21   s  of the substrate  21 . Therefore, when a first element is described herein to be at a higher level than a second element, the first element may be further from the lower surface  21   s  than the second element in the direction that is perpendicular to the lower surface  21   s.  Furthermore, when a first element is described herein to be at a lower level than a second element, the first element may be closer to the lower surface  21   s  than the second element in the direction that is perpendicular to the lower surface  21   s.  Furthermore, when a first element is described herein to be at a same level as a second element, the first element may be equally distant from/close to the lower surface  21   s  as the second element in the direction that is perpendicular to the lower surface  21   s.    
     The uppermost end  55   u  of the insulating pattern  55  may be farther from a lower surface  21   s  of the substrate  21  (e.g., may be at a higher level) than upper surfaces  51   u   1  and  52   u   1  of the first spacer layer  51  and the second spacer layer  52  adjacent to the first and second side surfaces  55 S 1  and  55 S 2 . Restated, the uppermost end  55   u  of the insulating pattern  55  may be farther from the lower surface  21   s  of the substrate  21 , in the direction that is perpendicular to the lower surface  21   s,  than a first upper surface  54   u   1  of the spacer layer  54  that is adjacent to the first and second side surfaces, where the first upper surface  54   u   1  may include either or both of the upper surfaces  51   u   1  and/or  52   u   1 . The distance, in the direction perpendicular to the lower surface  21   s,  between the upper surfaces  51   u   1  and/or  52   u   1  of the first spacer layer  51  and the second spacer layer  52  adjacent to the first and second side surfaces  55 S 1  and  55 S 2  and the uppermost end  55   u  of the insulating pattern  55  (e.g., the distance between the first upper surface  54   u   1  and the uppermost end  55   u ) may be about 10 nm to about 50 nm. In some example embodiments, the distance between the upper surfaces of the first spacer layer  51  and the second spacer layer  52  adjacent to the first and second side surfaces  55 S 1  and  55 S 2  and the uppermost end  55   u  of the insulating pattern  55  may be about 20 nm or more. 
     The first spacer layer  51  adjacent to the first and second side surfaces  55 S 1  and  55 S 2  may include an inclined upper surface  51   ui  that is inclined in a direction that is inclined to the lower surface  21   s  (where said direction may be non-perpendicular and non-parallel to the lower surface  21   s ). It will thus be understood that the spacer layer  54  that is adjacent to the first and second side surfaces  55 S 1  and  55 S 2  may include the inclined upper surface  51   ui.  The inclined upper surface  51   ui  may have an inclination descending as the inclined upper surface becomes farther from the insulating pattern  55 . The inclined upper surface  51   ui  may have an inclination that descends with distance from the insulating pattern  55  such that the level, in the direction perpendicular to the lower surface  21   s,  of a given portion of the inclined upper surface  51   ui  decreases in proportion to distance of the given portion of the inclined upper surface  51   ui  from the insulating pattern  55  in a direction that is parallel to the lower surface  21   s.  As shown in at least  FIG. 1 , the upper surface  52   u   1  of the second spacer layer  52  adjacent to the first and second side surfaces  55 S 1  and  55 S 2  may be nearer (e.g., closer) to the lower surface  21   s  of the substrate  21 , in the direction that is perpendicular to the lower surface  21   s,  than the upper surface  51   u   1  of the first spacer layer  51  adjacent to the first and second side surfaces  55 S 1  and  55 S 2 . The plurality of source/drain regions  60  may contact a side surface of the first spacer layer  51  and the upper surface  51   u   1  of the first spacer layer  51  while contacting the upper surface  52   u   1  of the second spacer layer  52 . As shown in at least  FIG. 1 , the source/drain regions  60  may contact (e.g., directly contact) the upper surfaces  51   u   1  and  52   u   1  of the first spacer layer  51  and the second spacer layer  52 . 
     The first spacer layer  51  and the second spacer layer  52  may extend between the insulating pattern  55  and the plurality of gate electrodes G 1  to G 3 . As shown in  FIG. 4 , the first spacer layer  51  and the second spacer layer  52  may have respective second upper surfaces  51   u   2  and  52   u   2  that are adjacent to the third and fourth side surfaces  55 S 3  and  55 S 4 . The second upper surfaces  51   u   2  and  52   u   2  may either, or collectively, be referred to as a second upper surface  54   u   2  of the spacer layer  54 . The uppermost end  55   u  of the insulating pattern  55  may be nearer to the lower surface  21   s  of the substrate  21  than an upper surface of the first spacer layer  51  adjacent to the third and fourth side surfaces  55 S 3  and  55 S 4 . Restated, and as shown in at least  FIG. 4 , the uppermost end  55   u  of the insulating pattern  55  may be nearer to the lower surface  21   s  of the substrate  21  than a second upper surface  51   u   2  of the first spacer layer  51  (and thus a second upper surface  54   u   2  of the spacer layer  54 ) adjacent to the third and fourth side surfaces  55 S 3  and  55 S 4 . An uppermost end of the first spacer layer  51  may be substantially coplanar with upper surfaces of the plurality of gate electrodes G 1  to G 3 . An upper surface of the second spacer layer  52  adjacent to the third and fourth side surfaces  55 S 3  and  55 S 4  may be nearer to the lower surface  21   s  of the substrate  21  than the uppermost end  55   u  of the insulating pattern  55 . 
     The first spacer layer  51 , the second spacer layer  52  and the insulating pattern  55  may include different materials, respectively. For example, each of the first spacer layer  51 , the second spacer layer  52  and the insulating pattern  55  may each include a material that is not included in any other of the first spacer layer  51 , the second spacer layer  52  and the insulating pattern  55  In some example embodiments, the first spacer layer  51  may include (e.g., partially or completely comprise) silicon oxycarbonitride (SiOCN), the second spacer layer  52  may include (e.g., partially or completely comprise) silicon oxide, and the insulating pattern  55  may include (e.g., partially or completely comprise) silicon nitride. In some example embodiments, the first spacer layer  51  may include (e.g., partially or completely comprise) silicon nitride, the second spacer layer  52  may include (e.g., partially or completely comprise) silicon oxide, and the insulating pattern  55  may include (e.g., partially or completely comprise) aluminum oxide such as Al 2 O 3 . In some example embodiments, the first spacer layer  51  may include (e.g., partially or completely comprise) silicon nitride, the second spacer layer  52  may include (e.g., partially or completely comprise) silicon oxide, and the insulating pattern  55  may include (e.g., partially or completely comprise) silicon oxycarbonitride (SiOCN). In some example embodiments, the insulating pattern  55  may include silicon nitride and the spacer layer  54  may include silicon oxycarbonitride (SiOCN). 
       FIGS. 6 and 7  are cross-sectional views explaining semiconductor devices according to some example embodiments of the inventive concepts.  FIG. 6  may be a cross-sectional view taken along line  2 - 2 ′ in  FIG. 5 .  FIG. 7  may be a cross-sectional view taken along line  3 - 3 ′ in  FIG. 5 . 
     Referring to  FIGS. 1, 4, 5, 6 and 7 , each of active regions F 1  to F 6  may have a vertical height greater than a horizontal width thereof. Each of the plurality of active regions F 1  to F 6  may include a fin shape. An upper surface of an element isolation layer  23  may be recessed to a lower level than upper ends of the plurality of active regions F 1  to F 6 . Each of the plurality of gate electrodes G 1  to G 3  may extend on the element isolation layer  23  while covering upper and side surfaces of a corresponding one of the plurality of active regions F 1  to F 6 . 
       FIGS. 8 and 9  are cross-sectional views explaining semiconductor devices according to some example embodiments of the inventive concepts.  FIG. 8  may be a cross-sectional view taken along line  1 - 1 ′ in  FIG. 5 .  FIG. 9  may be a cross-sectional view taken along line  4 - 4 ′ in  FIG. 5 . 
     Referring to  FIGS. 2, 3, 5, 8 and 9 , an upper surface  52   u   1  of a second spacer layer  52  adjacent to first and second side surfaces  55 S 1  and  55 S 2  may be farther from a lower surface  21   s  of a substrate  21 , in the direction that is perpendicular to the lower surface  21   s,  than an upper surface  51   u   1  of a first spacer layer  51  adjacent to the first and second side surfaces  55 S 1  and  55 S 2 . The first spacer layer  51  and the second spacer layer  52  adjacent to the first and second side surfaces  55 S 1  and  55 S 2  may include inclined upper surfaces, respectively. The inclined upper surfaces may have an inclination descending as the inclined upper surfaces become farther from an insulating pattern  55 . An upper surface of the second spacer layer  52  adjacent to third and fourth side surfaces  55 S 3  and  55 S 4  may be substantially coplanar with an upper surface of the insulating pattern  55 . 
       FIGS. 10 and 11  are cross-sectional views explaining semiconductor devices according to some example embodiments of the inventive concepts.  FIG. 10  may be a cross-sectional view taken along line  1 - 1 ′ in  FIG. 5 .  FIG. 11  may be a cross-sectional view taken along line  4 - 4 ′ in  FIG. 5 . 
     Referring to  FIGS. 2, 3, 5, 10 and 11 , each of a plurality of separation structures SP may include a first spacer layer  51  and an insulating pattern  55 . The first spacer layer  51  may partially cover lower and side surfaces of the insulating pattern  55 . The first spacer layer  51 , which is adjacent to first and second side surfaces  55 S 1  and  55 S 2 , may include an inclined upper surface. The inclined upper surface may have an inclination descending as the inclined upper surface becomes farther from the insulating pattern  55 . 
       FIGS. 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, and 24  are cross-sectional views taken along lines  1 - 1 ′,  2 - 2 ′,  3 - 3 ′ and  4 - 4 ′ in  FIG. 5 , to explain formation methods (e.g., methods of manufacture) of semiconductor devices according to some example embodiments of the inventive concepts. 
     Referring to  FIGS. 5 and 12 , an element isolation layer  23  may be formed on a substrate  21 , to define a plurality of active regions F 1  to F 6 . The plurality of active regions F 1  to F 6  may be spaced apart from one another. The plurality of active regions F 1  to F 6  may be parallel. Each of the active regions F 1  to F 6  may include a plurality of active patterns  31  to  35 . For example, the plurality of active patterns  31  to  35  may include a first active pattern  31 , a second active pattern  32 , a third active pattern  33 , a fourth active pattern  34 , and a fifth active pattern  35 . A plurality of sacrificial patterns  27  may be formed among the plurality of active patterns  31  to  35 . A plurality of temporary gate electrodes  41 ,  42 , and  43  may be formed to intersect the plurality of active regions F 1  to F 6 . A buffer layer  37  may be formed between the plurality of temporary gate electrodes  41 ,  42 , and  43  and the plurality of active regions F 1  to F 6 . A hard mask pattern  39  may be formed on the plurality of temporary gate electrodes  41 ,  42 , and  43 . 
     The substrate  21  may include a semiconductor substrate such as a silicon wafer or a silicon-on-insulator (SOI) wafer. The element isolation layer  23  may include an insulating layer formed using a shallow trench isolation (STI) method. The element isolation layer  23  may include silicon oxide, silicon nitride, silicon oxynitride, silicon boron nitride (SiBN), silicon carbon nitride (SiCN), low-k dielectrics, high-k dielectrics, or a combination thereof. 
     The first active pattern  31 , the second active pattern  32 , the third active pattern  33 , the fourth active pattern  34 , and the fifth active pattern  35  may be sequentially stacked. The plurality of sacrificial patterns  27  may be interposed among the first active pattern  31 , the second active pattern  32 , the third active pattern  33 , the fourth active pattern  34 , and the fifth active pattern  35 . In some example embodiments, the second active pattern  32 , the third active pattern  33 , the fourth active pattern  34 , and the fifth active pattern  35  may include monocrystalline silicon formed using an epitaxial growth method. The plurality of sacrificial patterns  27  may include SiGe formed using an epitaxial growth method. 
     An upper surface of the element isolation layer  23  may be recessed to a lower level than upper ends of the plurality of active regions F 1  to F 6 . In some example embodiments, the upper surface of the element isolation layer  23  may be formed at a lower level than an uppermost end of the first active pattern  31 . The first active pattern  31  may be defined in the substrate  21  by the element isolation layer  23 . In some example embodiments, the first active pattern  31  may include monocrystalline silicon. 
     The plurality of active patterns  31  to  35  may include P-type or N-type impurities. In some example embodiments, the first active pattern  31 , the second active pattern  32 , the third active pattern  33 , the fourth active pattern  34 , and the fifth active pattern  35  may include monocrystalline silicon including N-type impurities. 
     The buffer layer  37  may include silicon oxide. The plurality of temporary gate electrodes  41 ,  42 , and  43  may be parallel. Each of the plurality of temporary gate electrodes  41 ,  42 , and  43  may cover upper and side surfaces of the plurality of active regions F 1  to F 6 . Each of the plurality of temporary gate electrodes  41 ,  42 , and  43  may extend on the element isolation layer  23 . The plurality of temporary gate electrodes  41 ,  42 , and  43  may include polysilicon. The hard mask pattern  39  may include silicon oxide, silicon nitride, silicon oxynitride, or a combination thereof. 
     Referring to  FIGS. 5 and 13 , a first spacer layer  51  may be formed to conformally cover the element isolation layer  23 , the plurality of active regions F 1  to F 6 , the plurality of temporary gate electrodes  41 ,  42 , and  43  and the hard mask pattern  39 . The first spacer layer  51  may include silicon oxycarbonitride (SiOCN), silicon oxide, silicon nitride, silicon oxynitride, silicon boron nitride (SiBN), silicon carbon nitride (SiCN), low-k dielectrics, high-k dielectrics, or a combination thereof. 
     In some example embodiments, the first spacer layer  51  may include a material having etch selectivity with respect to the plurality of temporary gate electrodes  41 ,  42 , and  43  and the buffer layer  37 . The first spacer layer  51  may include a material different from those of the plurality of temporary gate electrodes  41 ,  42 , and  43  and the buffer layer  37 . The first spacer layer  51  may include silicon oxycarbonitride (SiOCN) or silicon nitride. The first spacer layer  51  may extend on the element isolation layer  23  while covering side surfaces of the plurality of active regions F 1  to F 6 , the buffer layer  37  and the plurality of temporary gate electrodes  41 ,  42 , and  43 . 
     Referring to  FIGS. 5 and 14 , a second spacer layer  52  may be formed to conformally cover the first spacer layer  51 . The second spacer layer  52  may include silicon oxide, silicon nitride, silicon oxynitride, silicon boron nitride (SiBN), silicon carbon nitride (SiCN), silicon oxycarbonitride (SiOCN), low-k dielectrics, high-k dielectrics, or a combination thereof. In some example embodiments, the second spacer layer  52  may include a material having etch selectivity with respect to the first spacer layer  51 . The second spacer layer  52  may include a material different from that of the first spacer layer  51 . The second spacer layer  52  may include silicon oxide. The second spacer layer  52  may be omitted. 
     Referring to  FIGS. 5 and 15 , a sacrificial mold layer  53  may be formed on the second spacer layer  52 . The sacrificial mold layer  53  may include a material having etch selectivity with respect to the first spacer layer  51  and the second spacer layer  52 . The sacrificial mold layer  53  may include spin-on hardmasks (SOH). Formation of the sacrificial mold layer  53  may include a coating process and an etch-back process. The sacrificial mold layer  53  may be reserved among the plurality of active regions F 1  to F 6 . An upper surface of the second spacer layer  52  may be partially exposed. 
     Referring to  FIGS. 5 and 16 , the first spacer layer  51  may be partially exposed through partial removal of the second spacer layer  52 . The second spacer layer  52  may be reserved between the first spacer layer  51  and the sacrificial mold layer  53 . The second spacer layer  52  may be exposed through removal of the sacrificial mold layer  53 . 
     Referring to  FIGS. 5 and 17 , an insulating layer  55 L may be formed to cover the first spacer layer  51  and the second spacer layer  52 . The insulating layer  55 L may include silicon oxide, silicon nitride, silicon oxynitride, silicon boron nitride (SiBN), silicon carbon nitride (SiCN), silicon oxycarbonitride (SiOCN), metal oxide, low-k dielectrics, high-k dielectrics, or a combination thereof. 
     In some example embodiments, the insulating layer  55 L may include a material having etch selectivity with respect to the first spacer layer  51  and the second spacer layer  52 . The insulating layer  55 L may include a material different from those of the first spacer layer  51  and the second spacer layer  52 . For example, the first spacer layer  51  may include silicon oxycarbonitride (SiOCN), the second spacer layer  52  may include silicon oxide, and the insulating layer  55 L may include silicon nitride. The first spacer layer  51  may include silicon nitride, the second spacer layer  52  may include silicon oxide, and the insulating layer  55 L may include aluminum oxide such as Al 2 O 3 . The first spacer layer  51  may include silicon nitride, the second spacer layer  52  may include silicon oxide, and the insulating layer  55 L may include silicon oxycarbonitride (SiOCN). 
     Referring to  FIGS. 5 and 18 , a plurality of insulating patterns  55  may be formed through partial removal of the insulating layer  55 L. Formation of the plurality of insulating patterns  55  through partial removal of the insulating layer  55 L may include an etch-back process. The plurality of insulating patterns  55  may be disposed among the plurality of active regions F 1  to F 6 . The second spacer layer  52  may surround lower and side surfaces of the plurality of insulating patterns  55 . 
     Referring to  FIGS. 5 and 19 , a plurality of drain trenches  60 T may be formed through partial removal of the plurality of active regions F 1  to F 6 . The plurality of drain trenches  60 T may be formed among the plurality of temporary gate electrodes  41 ,  42 , and  43 . Formation of the plurality of drain trenches  60 T through partial removal of the plurality of active regions F 1  to F 6  may include an anisotropic etching process, a directional etching process, an isotropic etching process, or a combination thereof. Side surfaces of the plurality of active patterns  31  to  35  and the plurality of sacrificial patterns  27  may be exposed at side walls of the plurality of drain trenches  60 T. Bottoms of the plurality of drain trenches  60 T may be formed at a lower level than an upper end of the first active pattern  31 . The first active pattern  31  or the substrate  21  may be exposed at the bottoms of the plurality of drain trenches  60 T. 
     The first spacer layer  51  and the second spacer layer  52  may be partially removed during formation of the plurality of drain trenches  60 T through partial removal of the plurality of active regions F 1  to F 6 . The first spacer layer  51  may be reserved on side surfaces of the hard mask pattern  39 , the plurality of temporary gate electrodes  41 ,  42 , and  43  and the buffer layer  37 . The first spacer layer  51  may be partially reserved on side surfaces of the plurality of insulating patterns  55 . The first spacer layer  51  may be reserved between the element isolation layer  23  and the plurality of insulating patterns  55 . The first spacer layer  51  may be reserved at a higher level than the bottoms of the plurality of drain trenches  60 T. 
     The second spacer layer  52  may be reserved between the first spacer layer  51  and the plurality of insulating patterns  55 . The first spacer layer  51 , the second spacer layer  52  and the plurality of insulating patterns  55  may constitute a plurality of separation structures SP. 
     In some example embodiments, upper surfaces of the first spacer layer  51  and the second spacer layer  52  may be formed at a lower level than upper ends of the plurality of insulating patterns  55 . The first spacer layer  51  and the plurality of insulating patterns  55  may be exposed at the side surfaces of the plurality of drain trenches  60 T. The first spacer layer  51  may include an inclined upper surface. The inclined upper surface of the first spacer layer  51  may have an inclination descending as the inclined upper surface becomes farther from the plurality of insulating patterns  55 . The upper surface of the second spacer layer  52  may be recessed to a lower level than the upper surface of the first spacer layer  51 . 
     In some example embodiments, each of the plurality of insulating patterns  55  may include a first side surface  55 S 1 , a second side surface  55 S 2 , a third side surface  55 S 3 , and a fourth side surface  55 S 4 . The second side surface  55 S 2  may face the first side surface  55 S 1 . Each of the first side surface  55 S 1  and the second side surface  55 S 2  may be adjacent to a corresponding one of the plurality of drain trenches  60 T. The fourth side surface  55 S 4  may face the third side surface  55 S 3 . Each of the third side surface  55 S 3  and the fourth side surface  55 S 4  may be adjacent to a corresponding one of the plurality of temporary gate electrodes  41 ,  42 , and  43 . 
     Referring to  FIGS. 5 and 20 , a plurality of insulating plugs  59  may be formed on side surfaces of the plurality of sacrificial patterns  27 . The plurality of insulating plugs  59  may include silicon oxide, silicon nitride, silicon oxynitride, low-k dielectrics, high-k dielectrics, or a combination thereof. 
     In some example embodiments, formation of the plurality of insulating plugs  59  may include selectively etching the side surfaces of the plurality of sacrificial patterns  27  exposed at the side surfaces of the plurality of drain trenches  60 T. Formation of the plurality of insulating plugs  59  may include an insulating thin film formation process and an anisotropic etching process. The plurality of insulating plugs  59  and the plurality of active patterns  31  to  35  may be exposed at the side walls of the plurality of drain trenches  60 T. 
     Referring to  FIGS. 5 and 21 , a plurality of source/drain regions  60  may be formed in the plurality of drain trenches  60 T. Formation of the plurality of source/drain regions  60  may include a selective epitaxial growth process. The plurality of source/drain regions  60  may include SiGe, SiC, Si, or a combination thereof. 
     In some example embodiments, each of the source/drain regions  60  may include a first layer  61 , a second layer  62 , and a third layer  63 . The first layer  61  may cover the plurality of active patterns  31  to  35 . The first layer  61  may directly contact the plurality of active patterns  31  to  35 . The first layer  61  may include SiGe, Si, or a combination thereof. The second layer  62  may be formed on the first layer  61 . The second layer  62  may be thicker than the first layer  61 . The second layer  62  may include SiGe. The parts by weight of Ge in the first layer  61  may be smaller than the parts by weight of Ge in the second layer  62 . The third layer  63  may be formed on the second layer  62 . The third layer  63  may include SiGe, Si, or a combination thereof. The parts by weight of Ge in the third layer  63  may be smaller than the parts by weight of Ge in the second layer  62 . In some example embodiments, the third layer  63  may include an Si layer. 
     In some example embodiments, each of the plurality of source/drain regions  60  may protrude to a higher level than uppermost ends of the plurality of active patterns  31  to  35 . The plurality of source/drain regions  60  may contact side surfaces of the plurality of separation structures SP. Each of the plurality of source/drain regions  60  may protrude to a higher level than uppermost ends of the plurality of separation structures SP. The plurality of source/drain regions  60  may be separated from one another by the plurality of separation structures SP. 
     Referring to  FIGS. 5 and 22 , an interlayer insulating layer  65  may be formed to cover the plurality of source/drain regions  60  and the plurality of separation structures SP. Upper surfaces of the plurality of temporary gate electrodes  41 ,  42 , and  43  may be exposed using a planarization process. The planarization process may include a chemical mechanical polishing (CMP) process. The interlayer insulating layer  65  may include silicon oxide, silicon nitride, silicon oxynitride, low-k dielectrics, high-k dielectrics, or a combination thereof. An upper surface of the interlayer insulating layer  65  and the upper surfaces of the first spacer layer  51  and the plurality of temporary gate electrodes  41 ,  42 , and  43  may be exposed on substantially the same plane. The interlayer insulating layer  65  may cover the plurality of insulating patterns  55 . The interlayer insulating layer  65  may directly contact the plurality of insulating patterns  55 . 
     Referring to  FIGS. 5 and 23 , a plurality of gate trenches  40 T and a plurality of gap regions  27 G may be formed through removal of the plurality of temporary gate electrodes  41 ,  42 , and  43 , the buffer layer  37  and the plurality of sacrificial patterns  27 . The plurality of gap regions  27 G may be formed among the plurality of active regions F 1  to F 6 . The plurality of gap regions  27 G may communicate with the plurality of gate trenches  40 T. 
     Referring to  FIGS. 5 and 24 , a gate dielectric layer  71  and a plurality of gate electrodes G 1  to G 3  may be formed in the plurality of gap regions  27 G and the plurality of gate trenches  40 T. The gate dielectric layer  71  may include silicon oxide, silicon nitride, silicon oxynitride, high-k dielectrics, or a combination thereof. The gate dielectric layer  71  may include a single layer or multiple layers. In some example embodiments, the gate dielectric layer  71  may include a silicon oxide layer, an LaO layer on the silicon oxide layer, and a high-k dielectric layer, such as an HfO layer, on the LaO layer. 
     The plurality of gate electrodes G 1  to G 3  may include metal, metal nitride, metal oxide, metal silicide, conductive carbon, polysilicon, or a combination thereof. The plurality of gate electrodes G 1  to G 3  may include a single layer or multiple layers. In some example embodiments, each of the plurality of gate electrodes G 1  to G 3  may include a workfunction metal layer or a gate conductive layer. The workfunction metal layer may include Ti, TiN, Ta, TaN, or a combination thereof. The gate conductive layer may include W, WN, Ti, TiN, Ta, TaN, Ru, or a combination thereof. Each of the plurality of gate electrodes G 1  to G 3  may correspond to a replacement metal gate electrode. 
       FIGS. 25 and 26  may be cross-sectional views taken along lines  1 - 1 ′,  2 - 2 ′,  3 - 3 ′ and  4 - 4 ′ in  FIG. 5 , to explain formation methods of semiconductor devices according to some example embodiments of the inventive concepts. 
     Referring to  FIGS. 5 and 25 , each of a plurality of active regions F 1  to F 6  may have a vertical height greater than a horizontal width thereof. Each of the plurality of active regions F 1  to F 6  may include a fin shape. An upper surface of an element isolation layer  23  may be recessed to a lower level than upper ends of the plurality of active regions F 1  to F 6 . Each of a plurality of temporary gate electrodes  41 ,  42 , and  43  may extend on the element isolation layer  23  while covering upper and side surfaces of a corresponding one of the plurality of active regions F 1  to F 6 . A buffer layer  37  may be formed between the plurality of temporary gate electrodes  41 ,  42 , and  43  and the plurality of active regions F 1  to F 6  and between the plurality of temporary gate electrodes  41 ,  42 , and  43  and the element isolation layer  23 . 
     Referring to  FIGS. 5 and 26 , each of a plurality of gate electrodes G 1  to G 3  may extend on the element isolation layer  23  while covering the upper and side surfaces of a corresponding one of the plurality of active regions F 1  to F 6 . A gate dielectric layer  71  may be formed between the plurality of gate electrodes G 1  to G 3  and the plurality of active regions F 1  to F 6  and between the plurality of gate electrodes G 1  to G 3  and the element isolation layer  23 . 
       FIGS. 27 and 28  may be cross-sectional views taken along lines  1 - 1 ′,  2 - 2 ′,  3 - 3 ′ and  4 - 4 ′ in  FIG. 5 , to explain formation methods of semiconductor devices according to some example embodiments of the inventive concepts. 
     Referring to  FIGS. 5 and 27 , an upper surface of a second spacer layer  52  adjacent to first and second side surfaces  55 S 1  and  55 S 2  may be farther from a lower surface  21   s  of the substrate  21  than an upper surface of a first spacer layer  51  adjacent to the first and second side surfaces  55 S 1  and  55 S 2 . The first spacer layer  51  and the second spacer layer  52  adjacent to the first and second side surfaces  55 S 1  and  55 S 2  may include inclined upper surfaces, respectively. The inclined upper surfaces may have an inclination descending as the inclined upper surfaces become farther from an insulating pattern  55 . An upper surface of the second spacer layer  52  adjacent to third and fourth side surfaces  55 S 3  and  55 S 4  may be substantially coplanar with an upper surface of the insulating pattern  55 . 
     Referring to  FIGS. 5 and 28 , the upper surface of the second spacer layer  52  adjacent to the first and second side surfaces  55 S 1  and  55 S 2  may protrude to a higher level than the upper surface of the first spacer layer  51  adjacent to the first and second side surfaces  55 S 1  and  55 S 2 . 
       FIG. 29  may be a cross-sectional view taken along lines  1 - 1 ′,  2 - 2 ′,  3 - 3 ′ and  4 - 4 ′ in  FIG. 5 , to explain formation methods of semiconductor devices according to some example embodiments of the inventive concepts. 
     Referring to  FIGS. 5 and 29 , each of a plurality of active regions F 1  to F 6  may have a vertical height greater than a horizontal width thereof. An upper surface of an element isolation layer  23  may be recessed to a lower level than upper ends of the plurality of active regions F 1  to F 6 . Each of the plurality of gate electrodes G 1  to G 3  may extend on the element isolation layer  23  while covering upper and side surfaces of a corresponding one of the plurality of active regions F 1  to F 6 . An upper surface of a second spacer layer  52  adjacent to first and second side surfaces  55 S 1  and  55 S 2  may protrude to a higher level than an upper surface of a first spacer layer  51  adjacent to the first and second side surfaces  55 S 1  and  55 S 2 . 
       FIGS. 30 and 31  may be cross-sectional views taken along lines  1 - 1 ′,  2 - 2 ′,  3 - 3 ′ and  4 - 4 ′ in  FIG. 5 , to explain formation methods of semiconductor devices according to some example embodiments of the inventive concepts. 
     Referring to  FIGS. 5 and 30 , a plurality of insulating patterns  55  may be formed on a first spacer layer  51 . The plurality of insulating patterns  55  may be disposed among a plurality of active regions F 1  to F 6 . The first spacer layer  51  may surround side and lower surfaces of the plurality of insulating patterns  55 . The first spacer layer  51  may extend between the element isolation layer  23  and the plurality of insulating patterns  55 . 
     Referring to  FIGS. 5 and 31 , each of a plurality of separation structures SP may include the first spacer layer  51  and the insulating pattern  55 . The first spacer layer  51  may partially cover lower and side surfaces of the insulating pattern  55 . The first spacer layer  51 , which is adjacent to first and second side surfaces  55 S 1  and  55 S 2 , may include an inclined upper surface. The inclined upper surface may have an inclination descending as the inclined upper surface becomes farther from the insulating pattern  55 . 
       FIG. 32  may be a cross-sectional view taken along lines  1 - 1 ′,  2 - 2 ′,  3 - 3 ′ and  4 - 4 ′ in  FIG. 5 , to explain formation methods of semiconductor devices according to some example embodiments of the inventive concepts. 
     Referring to  FIGS. 5 and 32 , each of a plurality of active regions F 1  to F 6  may have a vertical height greater than a horizontal width thereof. An upper surface of an element isolation layer  23  may be recessed to a lower level than upper ends of the plurality of active regions F 1  to F 6 . Each of a plurality of gate electrodes G 1  to G 3  may extend on the element isolation layer  23  while covering upper and side surfaces of a corresponding one of the plurality of active regions F 1  to F 6 . Each of a plurality of separation structures SP may include the first spacer layer  51  and the insulating pattern  55 . 
     In accordance with the some example embodiments of the inventive concepts, a separation structure may be provided among a plurality of source/drain regions. The separation structure may include an insulating pattern and a spacer layer. An uppermost end of the insulating pattern protrudes to a higher level than an upper surface of the spacer layer. It may be possible to realize semiconductor devices having excellent electrical characteristics while being advantageous in terms of mass production efficiency. 
     While the embodiments of the inventive concepts have been described with reference to the accompanying drawings, it should be understood by those skilled in the art that various modifications may be made without departing from the scope of the inventive concepts and without changing essential features thereof. Therefore, the above-described embodiments should be considered in a descriptive sense only and not for purposes of limitation.