Image Number 4 for United States Patent #6670650.
A high-speed, soft-recovery semiconductor device that reduces leakage current by increasing the Schottky ratio of Schottky contacts to pn junctions. In one embodiment of the present invention, an n.sup.- drift layer is formed on an n.sup.+ cathode layer 1 by epitaxial growth, and ring-shaped ring trenches having a prescribed width are formed in the n.sup.- drift layer. Oxide films are formed on the side walls of each ring trench. The ring trenches are arranged such that the centers of the rings of the ring trenches adjacent to one another form a triangular lattice unit. A p.sup.- anode layer is formed at the bottom of each ring trench. Schottky contacts are formed at the interface between an anode electrode and the surface of the n.sup.- drift layer. Ohmic contact is established between the surfaces of polysilicon portions and the anode electrode.