An integrated circuit device may include a gate insulation layer covering a top surface and opposite sidewalls of a fin-shaped active region, a gate electrode covering the gate insulation layer and a hydrogen atomic layer disposed along an interface between the fin-shaped active region and the gate insulation layer. A method of manufacturing the integrated circuit device may include forming an insulating layer covering a lower portion of a preliminary fin-shaped active region, forming a fin-shaped active region having an outer surface with an increased smoothness through annealing an upper portion of the preliminary fin-shaped active region in a hydrogen atmosphere and forming a hydrogen atomic layer covering the outer surface of the fin-shaped active region. A gate insulation layer and a gate electrode may be formed to cover a top surface and opposite sidewalls of the fin-shaped active region.