An interconnect is provided in a first insulating layer and the upper surface of the interconnect is higher than the upper surface of the first insulating layer. An air gap is disposed between the interconnect and the first insulating layer. An etching stopper film is formed over the first insulating layer, the air gap, and the interconnect. A second insulating layer is formed over the etching stopper film. A via is provided in the second insulating layer and is connected to the interconnect. A portion of the etching stopper film that is disposed over the air gap is thicker than another portion that is disposed over the interconnect.