Semiconductor device including semiconductor substrate, silicon carbide semiconductor layer, first electrode and second electrode

A semiconductor device, comprising:

• a semiconductor substrate of a first conductivity type, having a first principal surface and a second principal surface opposite to the first principal surface;
• a silicon carbide semiconductor layer of the first conductivity type, disposed on the first principal surface of the semiconductor substrate;
• a termination region of a second conductivity type, disposed within the silicon carbide semiconductor layer;
• a first electrode disposed on the silicon carbide semiconductor layer;
• and
• a second electrode disposed on the second principal surface of the semiconductor substrate and forming an ohmic junction with the semiconductor substrate, wherein:
• the semiconductor device has nonlinear current-voltage characteristics when a voltage is applied between the first electrode and the second electrode to make the first electrode more positive than the second electrode,
• the semiconductor device satisfies 1<dRf150/dRf25<1.5, where dRf25 is a ratio of a first voltage increase to a first current increase at 25° C. and dRf150 is a ratio of a second voltage increase to a second current increase at 150° C. in an on-state region of the nonlinear current-voltage characteristics,
• the termination region includes a guard ring region and an electrically floating region enclosing the guard ring region in the plan view;
• the first electrode includes a first part and two second parts surrounding the first part in a cross sectional view,
• the first part is directly contacts with the silicon carbide semiconductor layer without contacting the terminal region,
• each of the two second parts includes:
• a first portion directly in contact with the guard ring region,
• a second portion separated from the silicon carbide semiconductor layer by an insulating film, and
• an inclined portion extending from the first portion to the second portion along an edge of the insulating film at an angle less than a right angle.