Semiconductor device

A semiconductor device, comprising:

• a semiconductor chip having a first main surface including an active region and a peripheral region surrounding the active region;
• a first trench formed in the active region;
• a first insulating film formed on an inner surface of the first trench;
• a first electrode formed in the first trench interfacing the first insulating film, and forming a channel in a portion of the semiconductor chip facing the first insulating film;
• a second trench formed in the peripheral region and having a width greater a width of the first trench, wherein the second trench extends along a first direction and a second direction intersecting the first direction, and wherein the second trench has a corner portion curved from the first direction to the second direction;
• a second insulating film formed on an inner surface of the second trench;
• and
• a second electrode formed in the second trench interfacing the second insulating film and electrically coupled to the first electrode, wherein
• the first insulating film has a first thin portion formed at the bottom of the first trench, the first thin portion being selectively thinner than other portions of the first insulating film, and wherein
• the second insulating film has a second thin portion formed at the bottom of the corner portion of the second trench, the second thin portion being thinner than other portions of the second insulating film and thicker than the first thin portion.