Abstract: A semiconductor device includes an active pattern on a substrate, a source/drain pattern on the active pattern, a channel pattern connected to the source/drain pattern, the channel pattern including semiconductor patterns stacked and spaced apart from each other, a gate electrode extending across the channel pattern, and inner spacers between the gate electrode and the source/drain pattern. The semiconductor patterns include stacked first and second semiconductor patterns. The gate electrode includes first and second portions, which are sequentially stacked between the substrate and the first and second semiconductor patterns, respectively. The inner spacers include first and second air gaps, between the first and second portions of the gate electrode and the source/drain pattern. The largest width of the first air gap is larger than that of the second air gap.

Abstract: A semiconductor device includes: a first active pattern on a substrate and including a first active fin and a second active fin; a device isolation layer defining the first active pattern; a gate electrode crossing the first active pattern; a first source/drain pattern and a second source/drain pattern on the first active fin and the second active fin, respectively; an inner fin spacer between the first and second source/drain patterns; and a buffer layer between the first and second active fins, wherein the inner fin spacer includes: a first inner spacer portion contacting the first source/drain pattern; a second inner spacer portion contacting the second source/drain pattern; and an inner extended portion extending from the first and second inner spacer portions, wherein the inner extended portion is between the first and second active fins, wherein the buffer layer has a dielectric constant higher than that of the inner fin spacer.

Abstract: A semiconductor device includes an active pattern on a substrate, a pair of source/drain patterns on the active pattern, a channel pattern between the pair of source/drain patterns, the channel pattern including semiconductor patterns stacked to be spaced apart from each other, and a gate electrode crossing the channel pattern and extending in a first direction. One of the pair of source/drain patterns includes a first semiconductor layer and a second semiconductor layer thereon. The first semiconductor layer is in contact with a first semiconductor pattern, which is one of the stacked semiconductor patterns. The largest widths of the first semiconductor pattern, the first semiconductor layer, and the second semiconductor layer in the first direction are a first width, a second width, a third width, respectively, and the second width is larger than the first width and smaller than the third width.