Semiconductor device with rapid reverse recovery characteristic

A semiconductor device comprising:

• a first conductivity type first semiconductor layer;
• a first conductivity type second semiconductor layer being formed on said first semiconductor layer, said second semiconductor layer having a lower impurity concentration of the first conductivity type than said first semiconductor layer;
• a second conductivity type third semiconductor layer being formed on said second semiconductor layer;
• a first main electrode formed over said third semiconductor layer;
• and
• a second main electrode formed under said first semiconductor layer;
• wherein the film thickness of said second semiconductor layer is set to satisfy both of a first condition that a depletion layer extending from a PN junction at an interface between said second semiconductor layer and said third semiconductor layer does not reach said first semiconductor layer when a reverse voltage of about ½ to ⅔ of the reverse-direction voltage blocking capability of said PN junction is applied to said first and second main electrodes, and a second condition that the depletion layer extending from said PN junction reaches said first semiconductor layer when a reverse voltage exceeding about ⅔ of said voltage blocking capability is applied to said first and second main electrodes.