A semiconductor device, including an active region defined in a semiconductor substrate; a first contact plug on the semiconductor substrate, the first contact plug being connected to the active region; a bit line on the semiconductor substrate, the bit line being adjacent to the first contact plug; a first air gap spacer between the first contact plug and the bit line; a landing pad on the first contact plug; a blocking insulating layer on the bit line; and an air gap capping layer on the first air gap spacer, the air gap capping layer vertically overlapping the first air gap spacer, the air gap capping layer being between the blocking insulating layer and the landing pad, an upper surface of the blocking insulating layer being at a height equal to or higher than an upper surface of the landing pad.