A semiconductor device may include a semiconductor layer including at least one unit device, a first interconnection on the semiconductor layer and electrically connected to the at least one unit device, a diffusion barrier layer on the first interconnection, an intermetallic dielectric layer on the diffusion barrier layer, a plug in a first region of the intermetallic dielectric layer and passing through the diffusion barrier layer so that a bottom surface thereof contacts the first interconnection, and a first dummy plug in a second region of the intermetallic dielectric layer, passing through the diffusion barrier layer, and disposed apart from the first interconnection so that a bottom surface of the first dummy plug does not contact the first interconnection.