Patent ID: 7250345

Claim:
A manufacturing method for a semiconductor device, comprising the steps of: preparing a semiconductor substrate of a first conductive type having a first main surface and a second main surface that are opposed to each other; forming a body region of a second conductive type in said first main surface of said semiconductor substrate; forming a source diffusion region of the first conductive type in said first main surface within said body region; forming a gate electrode so as to be opposed to, via a gate insulating film, said body region sandwiched between a region of the first conductive type of said semiconductor substrate, which becomes a drain diffusion region, and said source diffusion region; reducing the thickness of said semiconductor substrate to no less than 50 μm and no greater than 250 μm by removing said second main surface of said drain diffusion region after the formation of an insulating gate type field effect transistor portion having said drain diffusion region, said source diffusion region and said gate electrode; and forming an impurity diffusion region of the second conductive type in said second main surface of said semiconductor substrate after the removal of said second main surface.