An integrated circuit device includes a fin-type active area along a first horizontal direction on a substrate, a device isolation layer on opposite sidewalls of the fin-type active area, a gate structure along a second horizontal direction crossing the first horizontal direction, the gate structure being on the fin-type active area and on the device isolation layer, and a source/drain area on the fin-type active area, the source/drain area being adjacent to the gate structure, and including an outer blocking layer, an inner blocking layer, and a main body layer sequentially stacked on the fin-type active area, and each of the outer blocking layer and the main body layer including a Si1-xGex layer, where x≠0, and the inner blocking layer including a Si layer.