Patent ID: 8748975

Claim:
A switching element comprising: a semiconductor substrate; a gate insulating film covering an inner surface of a trench formed in an upper surface of the semiconductor substrate; a gate electrode disposed in an internal portion of the trench; an n-type first semiconductor region present in the semiconductor substrate and in contact with the gate insulating film on a side surface of the trench; a p-type second semiconductor region present in the semiconductor substrate and in contact with the gate insulating film on the side surface of the trench and formed below the first semiconductor region; an n-type third semiconductor region present in the semiconductor substrate and in contact with the gate insulating film on the side surface of the trench and formed below the second semiconductor region; a p-type fourth semiconductor region present in the semiconductor substrate and in contact with the second semiconductor region on a lower side of the second semiconductor region and opposing the gate insulating film via the third semiconductor region, this fourth semiconductor region containing boron; and a fifth semiconductor region present below the third semiconductor region in the semiconductor substrate and formed to be exposed on a lower surface of the semiconductor substrate; wherein at least a part of the third semiconductor region positioned between the fourth semiconductor region and the gate insulating film has a carbon concentration higher than that of the fifth semiconductor region.