An integrated circuit (IC) device includes a fin-type active region extending lengthwise in a first direction, a plurality of nanosheets overlapping each other in a second direction on a fin top surface of the fin-type active region, and a source/drain region on the fin-type active region and facing the plurality of nanosheets in the first direction. The plurality of nanosheets include a first nanosheet, which is closest to the fin top surface of the fin-type active region and has a shortest length in the first direction, from among the plurality of nanosheets. The source/drain region includes a source/drain main region and a first source/drain protruding region protruding from the source/drain main region. The first source/drain protruding region protrudes from the source/drain main region toward the first nanosheet and overlaps portions of the plurality of nanosheets in the second direction.