High withstand voltage semiconductor device

A high-withstanding voltage semiconductor device comprising:

• a first semiconductor layer of a first conductivity type having a first and a second main surface;
• a second semiconductor layer of a second conductivity type selectively formed on the first main surface of said first semiconductor layer and directly surrounded by at least one of a fourth semiconductor layer of a second conductivity type and said first semiconductor layer on the first main surface thereof, said second semiconductor layer having a first region having a relatively high injection efficiency and a second region having a relatively low injection efficiency, said first region being surrounded by said second region, and said fourth semiconductor layer having a lower injection efficiency than that of said second region;
• a third semiconductor layer of the first conductivity type formed on the second main surface of said first semiconductor layer;
• a first electrode formed on said second semiconductor layer of the second conductivity type and connected to said first region and said second region of said second semiconductor layer;
• and
• a second electrode formed on said third semiconductor layer of the first conductivity type.