Semiconductor device and method for manufacturing semiconductor device

A semiconductor device comprising:

• a semiconductor substrate comprising a first surface and a second surface opposite the first surface;
• an insulating layer disposed on the second surface of the semiconductor substrate, and comprising an opening partly exposing the second surface;
• a stack made of a gallium-nitride-based material, comprising an n-type epitaxial layer and a p-type epitaxial layer in sequence on the second surface of the semiconductor substrate, and comprising a side wall extending from the insulating layer and forming a smaller angle than a right angle together with the second surface of the semiconductor substrate, and a top surface joined to the side wall;
• an n-type barrier layer partly disposed on the top surface of the stack and being in contact with the n-type epitaxial layer;
• an anode electrode being in contact with the p-type epitaxial layer and the n-type barrier layer on the top surface of the stack, and being in contact with the p-type epitaxial layer on the side wall of the stack;
• and
• a cathode electrode disposed on the first surface,
• wherein the semiconductor substrate comprises
• an n-type region exposed by the opening of the insulating layer, and
• a p-type region disposed between the insulating layer and the n-type region, and being in contact with the n-type epitaxial layer.

A method for manufacturing a semiconductor device, comprising the steps of:

• preparing a semiconductor substrate comprising a first surface and a second surface opposite the first surface;
• forming a first insulating layer comprising an opening partly exposing the second surface onto the second surface of the semiconductor substrate;
• forming a second insulating layer separated from the first insulating layer onto the second surface of the semiconductor substrate;
• depositing, in sequence, a side n-type epitaxial layer, a first p-type epitaxial layer having a first impurity concentration, and a second p-type epitaxial layer having an impurity concentration higher than the first impurity concentration through selective epitaxial-growth of a gallium-nitride-based material on the second surface of the semiconductor substrate using the first insulating layer and the second insulating layer as growth masks to form a stack comprising an outer side wall extending from the first insulating layer and forming a smaller angle than a right angle together with the second surface of the semiconductor substrate, an inner side wall extending from the second insulating layer, and a top surface joining the outer side wall and the inner side wall together;
• forming an n-type contact layer in contact with the first p-type epitaxial layer onto the top surface of the stack;
• forming a source electrode portion being in contact with the n-type contact layer on the top surface of the stack, and being in contact with the second p-type epitaxial layer on the outer side wall of the stack;
• forming a drain electrode onto the first surface;
• forming a gate insulating film onto the inner side wall of the stack;
• and
• forming a gate electrode onto the gate insulating film.