Semiconductor device and manufacturing method of semiconductor device

A manufacturing method of a semiconductor device comprising the steps of:

• (a) forming a first semiconductor region of a first conductivity type surrounding a formation scheduled region of a drain region of the first conductivity type;
• (b) forming a second semiconductor region of a second conductivity type opposite to the first conductivity type surrounding a formation scheduled region of a source region of the first conductivity type;
• (c) forming a first insulating region in a semiconductor layer on a side close to the formation scheduled region of the drain region between the formation scheduled region of the source region and the formation scheduled region of the drain region;
• (d) forming a gate electrode via a gate insulating film on the semiconductor layer between the first insulating region and the formation scheduled region of the source region;
• and
• (e) introducing an impurity of the first conductivity type into the semiconductor layer of the formation scheduled region of the source region and the formation scheduled region of the drain region, thereby forming the source region and the drain region,
• the method further comprising the steps of:
• (f) forming a third semiconductor region of the second conductivity type below the first semiconductor region or the formation scheduled region of the first semiconductor region;
• and
• (g) forming a fourth semiconductor region of the second conductivity type between the third semiconductor region or a formation scheduled region of the third semiconductor region and the second semiconductor region or a formation scheduled region of the second semiconductor region,
• wherein the fourth semiconductor region overlaps an end part of the third semiconductor region on a side closer to the second semiconductor region, and the fourth semiconductor region overlaps an end part of the second semiconductor region on a side closer to the first semiconductor region.