A method for forming a semiconductor device includes forming an etch target layer, forming a sacrificial hard mask layer having a metal layer and a carbon-based material layer on the etch target layer, forming a photoresist pattern on the carbon-based material layer, etching the carbon-based material layer by the photoresist pattern until a remaining carbon-based material portion has a predetermined thickness, etching the remaining carbon-based material portion until a corresponding metal layer portion is exposed to form a carbon-based material pattern, and etching the metal layer by using the carbon-based material pattern to form a hard mask pattern for forming the pattern.