Insulated gate bipolar transistor

An insulated gate bipolar transistor comprising:

• a silicon carbide substrate;
• a drift layer made of single-crystal silicon carbide, disposed on/over one main surface of said silicon carbide substrate, and having n type conductivity;
• a well region having p type conductivity and disposed to include a first main surface of said drift layer opposite to said silicon carbide substrate;
• an emitter region having n type conductivity and disposed to include said first main surface within said well region;
• an emitter electrode disposed on said first main surface in contact with said emitter region;
• an insulating film formed of an insulator and disposed on said first main surface in contact with said well region;
• a gate electrode disposed on said insulating film;
• and
• a collector electrode disposed on the other main surface of said silicon carbide substrate,
• said silicon carbide substrate including
• a base layer made of silicon carbide and having p type conductivity, and
• a SiC layer made of single-crystal silicon carbide and disposed on said base layer,
• a defect density being discontinuous at a boundary existing between said base layer and said SiC layer,
• said base layer having a p type impurity concentration exceeding 1×1018 cm−3.