A semiconductor device includes a fin-type active area, nanosheets, a gate, a source/drain region, and insulating spacers. The fin-type active area protrudes from a substrate in a first direction. The nanosheets are spaced from an upper surface of the fin-type active area and include channel regions. The gate is over the fin-type active area. The source/drain region is connected to the nanosheets. The insulating spacers are in the fin-type active area and between the nanosheets. Air spaces are between the insulating spacers and the source/drain region based on positions of the insulating spacers.