Semiconductor devices

A semiconductor device comprising:

• a gate structure on a substrate, the gate structure extending in a second direction parallel to an upper surface of the substrate;
• a first source/drain layer and a second source/drain layer at opposite sides, respectively, in a first direction of the gate structure, the first direction being substantially parallel to the upper surface of the substrate and crossing the second direction, and a central portion in the first direction of an upper surface of each of the first source/drain layer and the second source/drain layer being lower than an edge portion in the first direction of the upper surface;
• and
• a first contact plug and a second contact plug on the first source/drain layer and the second source/drain layer, respectively,
• wherein the first contact plug contacts one edge portion of opposite edge portions of the upper surface of the first source/drain layer so that a center of the first contact plug is offset from a center of the one edge portion of the upper surface of the first source/drain layer, the one edge portion being proximal to the gate structure in the first direction, and
• wherein the second contact plug contacts one edge portion of opposite edge portions of the upper surface of the second source/drain layer so that a center of the second contact plug is offset from a center of the one edge portion of the upper surface of the second source/drain layer, the one edge portion being distal to the gate structure in the first direction.

A semiconductor device comprising:

• first gate structures on a substrate including a first region and a second region, the first gate structures being spaced apart from each other in a first direction by a first distance on the first region of the substrate, each of the first gate structures extending in a second direction, each of the first direction and the second direction being substantially parallel to an upper surface of the substrate, and the first direction crossing the second direction;
• a first source/drain layer on a portion of the substrate between the first gate structures, a central portion in the first direction of an upper surface of the first source/drain layer being lower than an edge portion in the first direction of the upper surface of the first source/drain layer;
• a first contact plug on the first source/drain layer, the first contact plug contacting the edge portion of the upper surface of the first source/drain layer so that a center of the first contact plug is offset from a center of the upper surface of the first source/drain layer;
• second gate structures on the substrate, the second gate structures being spaced apart from each other in the first direction by a second distance on the second region of the substrate, each of the second gate structures extending in the second direction;
• a second source/drain layer on a portion of the substrate between the second gate structures, a central portion in the first direction of an upper surface of the second source/drain layer not being lower than an edge portion in the first direction of the upper surface of the second source/drain layer;
• and
• a second contact plug on the second source/drain layer, the second contact plug contacting the central portion of the upper surface of the second source/drain layer.