Semiconductor device having silicon carbide layer provided on silicon carbide substrate

A semiconductor device comprising:

• a silicon carbide semiconductor substrate of a first conductivity type;
• a first silicon carbide layer of the first conductivity type provided on a front surface of the silicon carbide semiconductor substrate and having an impurity concentration lower than that of the silicon carbide semiconductor substrate;
• a first semiconductor region of a second conductivity type selectively provided in a surface layer on a first side of the first silicon carbide layer opposite a second side of the first silicon carbide layer facing the silicon carbide semiconductor substrate;
• a second semiconductor region of the first conductivity type selectively provided in a surface layer on a first side of the first semiconductor region opposite a second side of the first semiconductor region facing toward the silicon carbide semiconductor substrate;
• a third semiconductor region of the second conductivity type selectively provided in the surface layer on the first side of the first semiconductor region and having an impurity concentration higher than that of the first semiconductor region;
• a gate electrode provided, via a gate insulating film, on at least one portion of a surface of the first semiconductor region between the second semiconductor region and the first silicon carbide layer;
• an interlayer insulating film provided on the gate electrode;
• a source electrode provided on surfaces of the second semiconductor region and the third semiconductor region;
• and
• a drain electrode provided on a rear surface of the silicon carbide semiconductor substrate, wherein
• the third semiconductor region is thicker, in a depth direction, than the second semiconductor region, and
• a width of a first side of the third semiconductor region facing the first semiconductor region is narrower than a width of a second side of the third semiconductor region facing the source electrode, wherein
• a result of multiplying an impurity concentration of the first semiconductor region by a thickness of a region of the first semiconductor region between the third semiconductor region and the first silicon carbide layer is less than a result of multiplying the impurity concentration of the first silicon carbide layer by a thickness of a region of the first silicon carbide layer between the first semiconductor region and the silicon carbide semiconductor substrate.