Method of manufacturing a power semiconductor device using implants and solid diffusion source

Claim 1

A semiconductor device manufacturing method comprising the steps of: forming a semiconductor layer of the first conductivity type on a semiconductor substrate; forming a first semiconductor well region of the second conductivity type having a high impurity concentration in that specified region of said semi-conductor layer corresponding to the peripheral area of the semiconductor device; forming oxide films on the surfaces of said semiconductor layer and said first semiconductor well region; successively depositing gate electrodes and an insulating layer on said oxide films; removing said deposited gate electrodes and said deposited insulating film in specified areas to make openings for forming metal contacts; implanting ionic impurity atoms of the second conductivity type through said oxide films remaining in the openings for metal contacts, thereafter putting the implanted silicon through heat treatment, thus forming a plurality of second semiconductor well regions of the second conductivity type, the wells of which are shallow compared with said first semiconductor well region; removing said oxide film remaining in said opening for metal contacts excepting a specified part corresponding to the peripheral area of the semiconductor device; depositing a layer of a material containing impurities of the first conductivity type and etching away unnecessary parts of said layer to form side walls of said layer on the side faces of said gate electrodes; and annealing a silicon chip comprising said substrate to diffuse the impurities of the first conductivity type contained in said layer into said second semiconductor well regions excepting the region where the diffusion of said first conductivity type impurities is inhibited by the remaining oxide film, thus forming a plurality of third semiconductor well regions of the first conductivity type.