Abstract: A semiconductor device including a substrate extending in a first direction and a second direction perpendicular to the first direction, a first active pattern protruding from a top surface of the substrate and extending in the first direction, an isolation pattern covering a sidewall of the first active pattern on the substrate, first silicon patterns spaced apart from each other in a third direction on the first active pattern, the third direction perpendicular to the first direction and second direction, a first source/drain layer extending in the third direction from a top surface of the first active pattern on the first active pattern, and in contact with sidewalls of the first silicon patterns, wherein a sidewall of the first source/drain layer in the second direction has a constant inclination with respect to the top surface of the substrate, and a gate structure extending in the second direction while filling a gap between the first silicon patterns on the substrate.