Patent ID: 8420496

Claim:
A method of fabricating a semiconductor device, comprising the steps of: providing an anode portion at a first major surface of a semiconductor substrate of a first conduction type; and providing a cathode portion at a second major surface of said semiconductor substrate opposite to said first major surface, wherein the step of providing said cathode portion includes the steps of introducing an impurity of said first conduction type from said second major surface, and performing a heat treatment to provide a buffer layer of said first conduction type having an impurity concentration gradually decreasing as seen from said second major surface to a predetermined depth, at least one of the steps of providing said anode portion and providing said cathode portion including: introducing an impurity of a corresponding predetermined conduction type at a surface of said semiconductor substrate from said surface to a first depth to provide a first region of said semiconductor substrate having said impurity of said predetermined conduction type introduced therein; and melting a second, predetermined region having a second depth deeper than said first depth and including said first region to uniform said impurity of said predetermined conduction type in concentration from said surface through to said second depth to provide a stepwise impurity layer having a stepwise impurity concentration profile, and the step of melting is performed after the step of performing said heat treatment to provide said buffer layer.