An integrated circuit (IC) device includes a pair of fin-shaped active areas that are adjacent to each other with a fin separation area therebetween, the pair of fin-shaped active areas extend in a line, and a fin separation insulating structure in the fin separation area, wherein the pair of fin-shaped active areas includes a first fin-shaped active area having a first corner defining part of the fin separation area, and wherein the fin separation insulating structure includes a lower insulating pattern that covers sidewalls of the pair of fin-shaped active areas, and an upper insulating pattern on the lower insulating pattern to cover at least part of the first corner, the upper insulating pattern having a top surface at a level higher than a top surface of each of the pair of fin-shaped active areas.