A semiconductor device according to example embodiments of inventive concepts may include a substrate, source/drain regions extending perpendicular to an upper surface of the substrate, a plurality of nanosheets on the substrate and separated from each other, and a gate electrode and a gate insulating layer on the substrate. The nanosheets define channel regions that extend in a first direction between the source/drain regions. The gate electrode surrounds the nanosheets and extends in a second direction intersecting the first direction. The gate insulating layer is between the nanosheets and the gate electrode. A length of the gate electrode in the first direction may be greater than a space between adjacent nanosheets among the nanosheets.