A semiconductor device includes: a fin-type active area extending in a first direction protruding from a substrate; a plurality of nanosheet stacked structures; a blocking film covering a part of the upper surface and one sidewall of each of a pair of nanosheet stacked structures adjacent to both sides of the fin-type active area among the plurality of nanosheet stacked structures; a gate electrode extending in a second direction intersecting the first direction on the fin-type active area, the gate electrode including a real gate electrode surrounding the plurality of nanosheets and a dummy gate electrode disposed on the blocking film; and a gate dielectric layer between the real gate electrode and the plurality of nanosheets and between the dummy gate electrode and the blocking film.