A method for forming a semiconductor device is disclosed. The method for forming the semiconductor device includes forming a first sacrificial film over a target layer to be etched, forming a first partition mask over the first sacrificial film, forming a first sacrificial film pattern by etching the first sacrificial film using the first partition mask, forming a first spacer at a sidewall of the first sacrificial film pattern, and forming a first spacer pattern by removing the first sacrificial film pattern. The first partition mask includes a plurality of first line-shaped space patterns extending in a first direction. A width of at least one space pattern located at both edges from among the plurality of first space patterns is smaller than a width of each of other space patterns.