Method for manufacturing a depletion type double-diffused metal-oxide

Abstract

A method for manufacturing double-diffused metal-oxide-semiconductor field effect transistor (DMOSFET) device is to form an insulating layer having an opening in top surface on a semiconductor wafer, channel regions and well regions and source regions through two stage diffusions of impurity materials respectively of a different conductivity type from and the same conductivity type as the wafer and carried out through the opening, and further gate, source and drain electrodes are formed after masks provided on a surface area where the drain regions and the source electrode regions that are to be connected to the well regions and source regions and a further ion-implantation of an impurity material of the same conductivity type as the wafer into the channel regions, with the threshold voltage controlled to achieve a depletion type. The channel regions are relatively lower in the carrier concentration than the other parts in the well regions to achieve a high breakdown voltage notwithstanding that the device is of the depletion type.