US Patent 7906416 Method for manufacturing semiconductor device

A method for manufacturing a semiconductor device from a semiconductor wafer having a first major surface, a recess provided inside a periphery on opposite side of the first major surface and surrounded by the periphery, and a second major surface provided at bottom of the recess is provided. The method comprises: fitting into the recess a doping mask having selectively formed openings to selectively cover the second major surface with the doping mask; and selectively introducing dopant into the second major surface.