A semiconductor device according to one embodiment is provided with: a substrate; a stacked body provided on the substrate; and a pillar portion penetrating the stacked body. The pillar portion has a first film including a first material and a second material, and a second film provided on an inner side of the first film. The second material is a material that increases an etching rate of the first material as a composition rate relative to the first material is higher, and the composition rate gradually decreases from an upper part to a lower part of the first film.