An integrated circuit device includes a fin-type active area protruding from a substrate; a plurality of liners sequentially covering lower side walls of the fin-type active area; a device isolation layer covering the lower side walls of the fin-type active area with the plurality of liners between the device isolation layer and the fin-type active area; and a gate insulating layer extending to cover a channel region of the fin-type active area, the plurality of liners, and the device isolation layer, and including protrusions located on portions of the gate insulating layer which cover the plurality of liners.