Silicon carbide semiconductor device and method of manufacturing a silicon carbide semiconductor device

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

• forming a first semiconductor layer of a first conductivity type on a semiconductor substrate of the first conductivity type, the first semiconductor layer having an impurity concentration lower than an impurity concentration of the semiconductor substrate;
• forming a second semiconductor layer of a second conductivity type on a first side of the first semiconductor layer, opposite a second side of the first semiconductor layer facing toward the semiconductor substrate;
• selectively forming a first semiconductor region of the first conductivity type in a surface layer of the second semiconductor layer on a first side of the second semiconductor layer, opposite a second side of the second semiconductor layer facing toward the first semiconductor layer, the first semiconductor region having an impurity concentration higher than an impurity concentration of the semiconductor substrate;
• forming a gate electrode opposing at least a part of a surface of the second semiconductor layer between the first semiconductor region and the first semiconductor layer, across a gate insulating film;
• irradiating protons in a first region of the semiconductor substrate, the first region spanning at least 2 μm from a surface of the semiconductor substrate facing toward the first semiconductor layer, the protons irradiated and implanted in the first region having a concentration in a range from 1×1013/cm3 to 1×1015/cm3,
• irradiating protons in a second region of the first semiconductor layer, the second region spanning at least 3 μm from a surface of the first semiconductor layer on the second side of the first semiconductor layer facing toward the semiconductor substrate, the protons irradiated and implanted in the second region having a concentration of-the protons being in a range from 1×1013/cm3 to 1×1015/cm3;
• and
• forming a first electrode on surfaces of the first semiconductor region and the second semiconductor layer,
• wherein the first region corresponds to a portion of the semiconductor substrate, and protons are not implanted in another portion of the semiconductor substrate.