Provided is an integrated circuit device including: a plurality of fin-type active regions protruding from a top surface of a substrate and extending in a first horizontal direction; at least one semiconductor layer, each including a lower semiconductor layer and an upper semiconductor layer sequentially stacked on at least one of the plurality of fin-type active regions; and a plurality of gate electrodes extending in a second horizontal direction crossing the first horizontal direction on the plurality of fin-type active regions, wherein the lower semiconductor layer includes a same material as a material of the upper semiconductor layer, and wherein a semiconductor interface is provided between the lower semiconductor layer and the upper semiconductor layer.