Insulated gate semiconductor device and method for manufacturing the insulated gate semiconductor device

An insulated gate semiconductor device, comprising:

• a semiconductor substrate;
• a front electrode provided on a front surface of the semiconductor substrate;
• and
• a rear electrode provided on a rear surface of the semiconductor substrate,
• wherein
• the insulated gate semiconductor device is configured to switch a conducting path between the front electrode and the rear electrode, and
• the semiconductor substrate comprises:
• a first region of a first conductivity type being in contact with the front electrode;
• a second region of a second conductivity type being in contact with the front electrode and the first region;
• a third region of the first conductivity type separated from the first region by the second region;
• a plurality of gate trenches provided in the front surface and penetrating the second region so as to reach the third region;
• a plurality of fourth regions of the second conductivity type each of which is exposed on a bottom surface of the corresponding gate trench;
• a plurality of first circumferential trenches and a plurality of the second circumferential trenches which are provided in the front surface in a range outside the second region, the first circumferential trenches and the second circumferential trenches being repeatedly and alternately provided in the range outside the second region, and the second circumferential trenches having a depth deeper than a depth of the first circumferential trenches;
• fifth regions of the second conductivity type each of which is exposed on a bottom surface of the corresponding first circumferential trench;
• sixth regions of the second conductivity type each of which is exposed on a bottom surface of the corresponding second circumferential trench, front side end portions of the sixth regions being located on a rear side with respect to rear side end portions of the fifth regions;
• and
• a seventh region of the first conductivity type connected to the third region and separating the fifth regions from the sixth regions.