A semiconductor device including: an active pattern on a substrate, the active pattern including a recess, the recess having a “V” shape; a growth prevention pattern on the recess; gate structures on portions of the active pattern at opposite sides of the recess; channels spaced apart from each other in a vertical direction perpendicular to an upper surface of the substrate, each of the channels extending through one of the gate structures; and a source/drain layer on the growth prevention pattern, the source/drain layer contacting the channels.