A method for fabricating a semiconductor device includes forming a stacked structure including at least one sacrificial layer and at least one semiconductor layer alternately stacked on a substrate, forming a dummy gate structure on the stacked structure, etching a recess in the stacked structure using the dummy gate structure as a mask, etching portions of the sacrificial layer exposed by the recess to form an etched sacrificial layer, forming a first spacer film on the etched sacrificial layer, forming a second spacer film on the first spacer film, the second spacer film including a material different from a material of the first spacer film, removing a first portion of the second spacer film, such that a second portion of the second spacer film remains, and forming a third spacer film on the second portion of the second spacer film.