Semiconductor device and method of manufacturing semiconductor device

1. A semiconductor device comprising:

a semiconductor substrate of a first conductivity type, in which a cell region, a ballast resistor region which is a region being an outer edge of the cell region, and a termination region surrounding the ballast resistor region are defined;

a first insulating film arranged on a front surface of the semiconductor substrate, having a first opening in the cell region, and having at least one second opening in the ballast resistor region;

a second insulating film filled in the at least one second opening;

a first impurity layer of a second conductivity type arranged on the front surface of the semiconductor substrate below the first opening;

a second impurity layer of the second conductivity type arranged on the front surface of the semiconductor substrate below the at least one second opening; and

a conductive film arranged from the front surface of the first opening of the semiconductor substrate to the termination region.

2. The semiconductor device according to claim 1 , wherein

a depth of the first impurity layer, a thickness of the second insulating film, an opening width of the second opening, arrangement intervals between each of the at least second opening when a plurality of the second openings exist, and a gap between the first opening and the at least one second opening are defined based on a thickness of the first insulating film.

3. The semiconductor device according to claim 1 , wherein

a pattern of the at least one second opening is formed in a dot pattern in plan view.

4. The semiconductor device according to claim 1 , wherein

in the at least one second opening, a width in a corner portion is different from a width in other portions in the semiconductor substrate, and

an area of the first opening does not change in both cases where, in the at least one second opening, the width in the corner portion is and is not different from the width in the other portions in the semiconductor substrate.

5. The semiconductor device according to claim 1 , wherein

in the at least one second opening, a width in a corner portion is different from a width in other portions in the semiconductor substrate, and

an area of the first opening is greater than that in a case where, in the at least one second opening, the width in the corner portion is not different from the width in the other portions in the semiconductor substrate.

6. The semiconductor device according to claim 1 , wherein

the first insulating film has the at least one second opening and at least one third opening in the termination region,

a third impurity layer of the second conductivity type arranged on the front surface of the semiconductor substrate below the at least one third opening,

the second insulating film is filled in the at least one second opening, and

the conductive film is in contact with the third impurity layer through the at least third opening.

7. The semiconductor device according to claim 1 , further comprising:

a buffer layer of the first conductivity type arranged on a back surface of the semiconductor substrate; and

a fourth impurity layer of the first conductivity type arranged on the buffer layer.

8. The semiconductor device according to claim 1 , further comprising:

a fourth impurity layer of the first conductivity type arranged on the back surface of the semiconductor substrate; and

a fifth impurity layer of the second conductivity type arranged in a portion of the back surface of the semiconductor substrate from the termination region to a portion of the ballast resistor region and is adjacent to the fourth impurity layer.

9. The semiconductor device according to claim 1 , wherein

the semiconductor substrate has a lifetime killer level in the termination region.

10. The semiconductor device according to claim 1 , wherein

the first insulating film has a plurality of second openings,

a plurality of second impurity layers are arranged on the front surface of the plurality of second openings, and

each of the plurality of second impurity layers are adjacent to each other and the second impurity layer closest to the first impurity layer among the plurality of second impurity layers is in contact with the first impurity layer.

11. The semiconductor device according to claim 1 , wherein

a pattern of the plurality of second openings is formed in a striped pattern in plan view.

12. A method of manufacturing a semiconductor device, comprising:

preparing a semiconductor substrate of a first conductivity type, in which a cell region, a ballast resistor region which is a region being an outer edge of the cell region, and a termination region surrounding the ballast resistor region are defined;

forming a first insulating film having a first opening in the cell region, and having at least one second opening in the ballast resistor region, on a front surface of the semiconductor substrate;

implanting or depositing impurities of a second conductivity type in the semiconductor substrate through the first opening and the at least one second opening;

forming a first impurity layer of the second conductivity type on the front surface of the semiconductor substrate below the first opening and forming a second impurity layer of the second conductivity type on the front surface of the semiconductor substrate blow the at least one second opening by activating the implanted or deposited impurities;

filling a second insulating film in the at least one second opening; and

forming a conductive film from the front surface of the first opening of the semiconductor substrate to the termination region.