According to one embodiment, a method for manufacturing a semiconductor device includes forming a plurality of insulating isolation sections provided so as to extend in a first direction, isolate the stacked body in a second direction, and have a projection projecting from the stacked body. Each insulating isolation section has a side wall including recessed sections and projected sections repeated along the first direction. The method includes forming a sidewall film on a side wall of the projection of the insulating isolation section, and forming a plurality of first holes surrounded by the sidewall film and isolated by the sidewall film in the first direction, between the plurality of insulating isolation sections. The method includes forming a second hole in the stacked body provided under the first hole by etching with the insulating isolation section and the sidewall film used as a mask.