A method for manufacturing a semiconductor device includes: a first step of forming a base layer, which includes an element portion having a gate electrode and a flat interlayer insulating film formed so as to cover the gate electrode; a second step of ion implanting a delamination material into the base layer to form a delamination layer; a third step of bonding the base layer to a substrate; and a fourth step of separating and removing a part of the base layer along the delamination layer. An implantation depth of the delamination material in the gate electrode is substantially the same as that of the delamination material in the interlayer insulating film.