A semiconductor device includes: a fin-type active region protruding from a substrate and extending in a first direction; at least one nano-sheet spaced apart from an upper surface of the fin-type active region and facing the upper surface of the fin-type active region, the at least one nano-sheet having a channel region; a gate extending on the fin-type active region in a second direction crossing the first direction and surrounding at least a portion of the at least one nano-sheet; a source/drain region on the fin-type active region on both sides of the at least one nano-sheet; and a source/drain protection layer on a sidewall of the at least one nano-sheet and between the source/drain region and the at least one nano-sheet.