A semiconductor device includes a first interlayer dielectric film on a substrate, first and second wires respectively extending in a first direction within the first interlayer dielectric film, the first and second wires being adjacent to each other in a second direction different from the first direction, a hard mask pattern on the first interlayer dielectric film, the hard mask pattern including an opening, and an air gap within the first interlayer dielectric film, the air gap including a first portion overlapping vertically with the opening and a second portion not overlapping with the opening in the first direction.