A method for manufacturing a semiconductor device includes the steps of: forming a first gate stack on a semiconductor substrate, the first gate stack includes a first gate conductor and a first gate dielectric between the first gate conductor and the semiconductor substrate; forming source/drain regions on the semiconductor substrate; forming a multilayer structure including at least one sacrificial layer and at least one insulating layer under the sacrificial layer on the semiconductor substrate and the first gate stack; performing a first RIE on the multilayer structure; performing a second RIE on the multilayer structure; selectively etching the first gate stack with respect to the insulating layer, in which the first gate conductor is removed and an opening is formed in the insulating layer; and forming a second gate conductor in the opening.