Semiconductor device, and method of manufacturing semiconductor device

A semiconductor device comprising:

• an n-type semiconductor substrate;
• a p-type semiconductor region formed in a front surface side of the semiconductor substrate;
• and
• an n-type field stop region formed in a rear surface side of the semiconductor substrate;
• wherein
• a distribution graph in which an impurity density in a depth direction in the field stop region as shown in a common logarithm has a plurality of peaks including a first peak, a second peak that is closer to the rear surface side of the semiconductor substrate than the first peak, a third peak that is closer to the rear surface side of the semiconductor substrate than the second peak, and a fourth peak that is closer to the rear surface side of the semiconductor substrate than the third peak,
• each of the plurality of peaks including the first peak, the second peak, the third peak and the fourth peak has a peak maximum point, and peak end points including a first peak end point and a second peak end point formed at each side of the peak maximum point, the second peak end point being closer to the rear surface side of the semiconductor substrate than the first peak end point, and the second peak end point of the second peak is closer to the rear surface side of the semiconductor substrate than the first peak end point of the second peak,
• an impurity density of the second peak end point of the first peak is not lower than an impurity density of the second peak end point of the second peak in the distribution graph.

A method for manufacturing a semiconductor device comprising:

• preparing an n-type semiconductor substrate;
• forming a p-type semiconductor region in a front surface side of the semiconductor substrate;
• and
• forming an n-type field stop region in a rear surface side of the semiconductor substrate;
• wherein
• a distribution graph in which an impurity density in a depth direction in the field stop region as shown in a common logarithm comprises a plurality of peaks including a first peak, a second peak that is closer to the rear surface side of the semiconductor substrate than the first peak, a third peak that is closer to the rear surface side of the semiconductor substrate than the second peak, and a fourth peak that is closer to the rear surface side of the semiconductor substrate than the third peak,
• each of the plurality of peaks including the first peak, the second peak, the third peak and the fourth peak has a peak maximum point, and peak end points formed at each side of the peak maximum point including a first peak end point and a second peak end point, the first peak end point being closer to the front surface side of the semiconductor substrate than the second peak end point, and
• a first peak end point of the second peak is not lower than a second peak end point of the second peak.