Patent ID: 8502237

Claim:
A semiconductor rectifying device comprising: a first-conductive-type semiconductor substrate made of a wide bandgap semiconductor; a first-conductive-type semiconductor layer formed on an upper surface of the semiconductor substrate and made of the wide bandgap semiconductor, the semiconductor layer having an impurity concentration lower than that of the semiconductor substrate; a first-conductive-type first semiconductor region formed at a surface of the semiconductor layer and made of the wide bandgap semiconductor; a second-conductive-type second semiconductor region formed around the first semiconductor region and made of the wide bandgap semiconductor; a second-conductive-type third semiconductor region sandwiched between the first semiconductor region and made of the wide bandgap semiconductor, the third semiconductor region having a junction depth deeper than a junction depth of the second semiconductor region, the third semiconductor region having a junction depth not lower than 0.6 fold thickness of the semiconductor layer, an impurity concentration of the third semiconductor region is lower than an impurity concentration of the semiconductor substrate, and the impurity concentration of the third semiconductor region is one fold to ten fold an impurity concentration of the semiconductor layer; a first electrode formed on the first, second, and third semiconductor regions; and a second electrode formed on a lower surface of the semiconductor substrate, wherein a Schottky junction is established between the first electrode and the first semiconductor region, and an ohmic junction is established between the first electrode and the third semiconductor region.