Semiconductor device and manufacturing method therefor

A method for manufacturing a semiconductor device, the semiconductor device including a first region provided at a center of a semiconductor substrate and a second region provided outside the first region in a planar view, the method comprising the steps of:

• (a) providing the semiconductor substrate of a first conductive type having a first main surface and a second main surface opposite to the first main surface;
• (b) forming a plurality of first trenches extending in a first direction in the first region such that the first trenches are spaced apart from each other in a second direction perpendicular to the first direction at the first main surface, each of the first trenches having a first depth from the first main surface, and forming a plurality of second trenches in the second region such that the second trenches are spaced apart from each other in the second direction, each of the second trenches having a second depth from the first main surface and having a shape enclosed by a rectangular outer outline and a rectangular inner outline in plan view;
• (c) forming a first semiconductor region by ion-implanting impurities of a second conductive type different from the first conductive type, into a part of the semiconductor substrate in the second region located outside the second trenches and outside the outer outlines of the respective second trenches in plan view, the first semiconductor region having a third depth from the first main surface deeper than the second depth;
• (d) forming a first conductive film over the first main surface via a first insulating film to fill insides of the respective first trenches and the respective second trenches;
• (e) by processing the first conductive film using a patterned resist film as a mask, forming a plurality of first trench gate electrodes made of the first conductive film in the respective first trenches via the first insulating film, forming a plurality of second trench gate electrodes made of the first conductive film in the respective second trenches via the first insulating film, and forming an extraction electrode made of the first conductive film over the first main surface integrally with the second trench gate electrodes via the first insulating film;
• and
• (f) after forming an interlayer insulating film over the first main surface, forming a gate electrode over the interlayer insulating film, the gate electrode being electrically coupled to the extraction electrode,
• wherein each of the first trenches leads to any one of the second trenches, and the second trench gate electrodes are electrically coupled to the first trench gate electrodes.