High withstand voltage diode and power conversion device

A semiconductor device, comprising:

• an n-type drift layer;
• a first p-type anode layer provided on a surface of said n-type drift layer;
• at least one second p-type anode layer being selectively provided on a surface of said first p-type anode layer, including a donor impurity and an acceptor impurity, and having an acceptor impurity concentration lower than said first p-type anode layer;
• an n-type buffer layer provided on a rear surface of said n-type drift layer;
• and
• an n-type cathode layer and a p-type cathode layer provided to be adjacent to each other in a planar view on a surface of said n-type buffer layer, wherein
• a thickness of said n-type cathode layer is equal to or larger than a thickness of said p-type cathode layer,
• a thickness of said first p-type anode layer is equal to or larger than a thickness of said second p-type anode layer,
• a donor impurity concentration of said n-type cathode layer is equal to or larger than an acceptor impurity concentration of said p-type cathode layer,
• an acceptor impurity concentration of said first p-type anode layer is equal to or larger than a donor impurity concentration of said second p-type anode layer,
• an acceptor impurity concentration of said second p-type anode layer is equal to or larger than a donor impurity concentration of said second p-type anode layer, and
• a donor impurity concentration of said second p-type anode layer is equal to or larger than a donor impurity concentration of said n-type drift layer.