An integrated circuit (IC) device includes: a fin-type active area protruding from a substrate and extending in a first horizontal direction; a first nanosheet disposed above an upper surface of the fin-type active area with a first separation space therebetween; a second nanosheet disposed above the first nanosheet with a second separation space therebetween; a gate line extending on the substrate in a second horizontal direction intersecting the first horizontal direction, at least a portion of the gate line being disposed in the second separation space; and a bottom insulation structure disposed in the first separation space.