US Patent 7927952 Method of manufacturing semiconductor devices

A method of manufacturing semiconductor devices comprises forming an semiconductor layer of the first conduction type on a substrate of the first conduction type; forming an anti-oxidizing layer on the surface of the semiconductor layer of the first conduction type, the anti-oxidizing layer having an aperture only through a region for use in formation of a guard ring layer of the second conduction type; forming the guard ring layer of the second conduction type in the surface of the semiconductor layer of the first conduction type through implantation of ions into a surface where said anti-oxidizing layer is formed; forming an oxide layer at least in the aperture; forming a base layer of the second conduction type adjacent to the guard ring layer of the second conduction type in the surface of the semiconductor layer of the first conduction type; and forming a diffused layer of the first conduction type through implantation of ions into the base layer of the second conduction type.