Semiconductor device manufacturing method and semiconductor device

A semiconductor device manufacturing method, comprising:

• forming a silicon oxide film on a silicon carbide layer, an atomic concentration of oxygen (O) in the silicon oxide film being less than twice an atomic concentration of silicon (Si) in the silicon oxide film;
• forming a first silicon film on the silicon oxide film;
• performing a first heat treatment in an atmosphere containing nitrogen oxide gas after the forming the first silicon film;
• and
• forming a second silicon film containing boron (B) and thicker than the first silicon film after the first heat treatment.

A semiconductor device, comprising:

• a silicon carbide layer having a surface inclined by an angle equal to or more than 0 degrees and equal to or less than 8 degrees with respect to a {0001}face and including a trench;
• a gate electrode provided in the trench;
• a silicon oxide layer provided between the silicon carbide layer and the gate electrode;
• and
• a region provided between the silicon carbide layer and the silicon oxide layer and containing nitrogen (N) and at least one element selected from a group consisting of hydrogen (H), deuterium (D), and fluorine (F).

A semiconductor device, comprising:

• a silicon carbide layer;
• a gate electrode containing polycrystalline silicon containing boron (B);
• a silicon oxide layer provided between the silicon carbide layer and the gate electrode;
• a first region provided between the silicon carbide layer and the silicon oxide layer and containing nitrogen (N);
• and
• a second region provided between the silicon oxide layer and the gate electrode and containing nitrogen (N).