A method for fabricating a semiconductor device includes forming an insulating layer on a substrate; forming a first mask pattern including silicon on the insulating layer and forming a second mask pattern including an oxide on the first mask pattern; forming a coating layer that includes carbon and which covers an upper surface of the insulating layer, a sidewall of the first mask pattern, and the second mask pattern; removing a portion of the coating layer and the second mask pattern; forming a metal layer on an upper surface of the first mask pattern and on a sidewall of the coating layer; exposing the upper surface of the insulating layer by removing the coating layer; and etching the insulating layer by using the first mask pattern and the metal layer as a mask.