A semiconductor device includes a substrate; a hydrogen insulating layer disposed on the substrate and including hydrogen ions; a first level layer disposed on the substrate and including a first wire and a second wire; a second level layer disposed on the substrate at a different level from the first level layer and including a third wire; an interlayer insulating layer disposed between the first level layer and the second level layer; a diffusion prevention layer contacting the third wire; a contact plug penetrating the interlayer insulating layer and electrically connecting the second wire to the third wire; and a dummy contact plug penetrating the interlayer insulating layer. The dummy contact plug contacts the first and second level layers, is spaced apart from the diffusion prevention layer, and is configured to provide a movement path for the hydrogen ions in the hydrogen insulating layer.