Abstract: A method of fabricating a semiconductor device includes providing a substrate, forming a target film, a first mask film, a second mask film, and an upper mask pattern on the substrate, forming a first spacer pattern that includes a first line portion and a second line portion, and a folding portion that connects the first line portion and the second line portion, forming a slit mask pattern that partially covers the first spacer pattern, forming a first mask pattern by patterning the second mask film using the slit mask pattern and the first spacer pattern as an etching mask, forming a second spacer pattern, forming a second mask pattern by patterning the first mask film using the second spacer pattern as an etching mask, and forming a plurality of target patterns by patterning the target film using the second mask pattern as an etching mask.