Method of manufacturing silicon carbide semiconductor device

A method of manufacturing a silicon carbide semiconductor device, the method comprising:

• preparing a semiconductor substrate made of silicon carbide, the semiconductor substrate including a substrate, a drift layer, a base layer, and an impurity region, the substrate having a first conductivity, the drift layer having the first conductivity and formed on the substrate, the base layer having a second conductivity and formed on the drift layer, the impurity region having the first conductivity and formed at a surface layer portion of the base layer, the preparing of the semiconductor substrate including
• forming a gate insulation film at a portion of the base layer between the drift layer and the impurity region,
• forming a gate electrode on the gate insulation film, and
• forming a connection wiring above a surface of the semiconductor substrate at a side closer to the base layer, the connection wiring connected to the gate electrode and made of polysilicon;
• forming an interlayer insulation film to cover the base layer, the impurity region, the gate electrode, and the connection wiring;
• forming a first contact hole at a first region including the interlayer insulation film to expose the base layer and the impurity region;
• forming a second contact hole at a second region including the interlayer insulation film to expose the connection wiring;
• forming an oxide film at a portion of the connection wiring exposed from the second contact hole through thermal oxidation;
• forming a metal layer over the semiconductor substrate including a portion exposed from the first contact hole;
• forming a metal silicide film by reacting the metal layer with the semiconductor substrate through heating;
• removing an unreacted metal layer as a portion of the metal layer different from the metal silicide film;
• forming an electrode electrically directly connected to the base layer and the impurity region through the first contact hole;
• and
• forming a gate wiring electrically directly connected to the connection wiring through the second contact hole, the gate wiring having a portion made of material capable of deoxidizing the oxide film formed on the connection wiring to remove oxygen from the oxide film,
• wherein, in the forming of the gate wiring, the oxide film is removed by deoxidizing the oxide film to remove the oxygen from the oxide film into the gate wiring in the same process of heating treatment for the gate wiring,
• wherein the preparing of the semiconductor substrate further includes terminating a dangling bond at an interface between the semiconductor substrate and the gate insulation film with nitrogen after the forming of the gate electrode, and
• wherein, in the forming of the oxide film, the oxide film is formed to have a thickness in a range of 1 to 10 nanometers.