Patent ID: 7534665

Claim:
A method of manufacturing a semiconductor device, comprising the steps of: depositing sequentially a gate oxide film, a first silicon film, and a silicon nitride film on a surface of a semiconductor layer, and selectively removing the first silicon and the silicon nitride film so that an opening portion is provided over the semiconductor layer in a region in which a field oxide film is to be formed; depositing resist over the surface of the semiconductor layer, then selectively removing the resist using steps of the opening portion as alignment marks, and forming a drain diffusion layer using the resist as a mask; forming the field oxide film at the surface of the semiconductor layer using the silicon nitride film, removing at least the silicon nitride film, and then forming gate electrodes so that at least one ends of the gate electrodes are placed over the field oxide film; and forming a back-gate diffusion layer so that part of the back-gate diffusion layer is placed under other ends of the gate electrodes, and forming a source diffusion layer from a surface of the back-gate diffusion layer.