Semiconductor device

1. A semiconductor device, comprising:

a semiconductor substrate of a first conductivity type, the semiconductor substrate including a p-type base region on a front surface of the semiconductor substrate, and an n-type emitter region on the p-type base region;

a main transistor section in an active region on the semiconductor substrate; and

a sense transistor section outside the active region on the semiconductor substrate,

wherein the active region is provided with a main well region of a second conductivity type,

wherein the p-type base region is shallower and has lower concentration than the main well region,

wherein an emitter electrode is provided on the front surface of the semiconductor substrate, in contact with the p-type base region and the n-type emitter region,

wherein the sense transistor section has a sense gate trench section formed extending from the outside of the active region to the main well region on a front surface of the semiconductor substrate,

wherein the sense gate trench section penetrates through the p-type base region and the n-type emitter region, and

wherein a sense gate conductive section in the sense gate trench section is insulated from the emitter electrode.

2. The semiconductor device according to claim 1 , wherein the semiconductor substrate has:

a sense well region of a second conductivity type outside the active region; and

a well separation region of a first conductivity type that separates the sense well region and the main well region,

wherein the sense gate trench section is formed crossing the well separation region on the front surface of the semiconductor substrate.

3. The semiconductor device according to claim 1 , further comprising a diode provided in the active region on the semiconductor substrate, wherein the sense transistor section is provided at a position that does not oppose the diode.

4. The semiconductor device according to claim 2 , wherein the main transistor section has a main gate trench section electrically connected to the sense gate trench section.

5. The semiconductor device according to claim 4 , wherein the main gate trench section is provided within the semiconductor substrate separately from the sense gate trench section.

6. The semiconductor device according to claim 5 , further comprising a gate electrode provided over the main well region,

wherein the main gate trench section has a main gate trench formed on the front surface of the semiconductor substrate, and a main gate conductive section formed within the main gate trench,

wherein the sense gate trench section has a sense gate trench formed on the front surface of the semiconductor substrate, and a sense gate conductive section formed within the sense gate trench, and

wherein the gate electrode is in contact with both the main gate conductive section and the sense gate conductive section.

7. The semiconductor device according to claim 4 , wherein the main gate trench section is connected to the sense gate trench section within the semiconductor substrate.

8. The semiconductor device according to claim 7 , wherein the main gate trench section has a plurality of first trench sections provided extending in a predetermined extending direction, and a second trench section which is provided extending in a direction different from the extending direction and which connects two adjacent first trench sections.

9. The semiconductor device according to claim 8 , further comprising a gate electrode formed passing over the second trench section, and crossing over a plurality of the first trench sections.

10. The semiconductor device according to claim 4 , wherein on the semiconductor substrate, an emitter region adjacent to the sense gate trench section, and an emitter region which is formed at a position deeper than the emitter region adjacent to the sense gate trench section and which is adjacent to the main gate trench section are formed.

11. The semiconductor device according to claim 10 , wherein the sense gate trench section has a sense gate conductive section within a trench, wherein the main gate trench section has a main gate conductive section within a trench, and

wherein a distance from the front surface of the semiconductor substrate to an upper end of the sense gate conductive section is shorter than a distance from the front surface of the semiconductor substrate to an upper end of the main gate conductive section.

12. The semiconductor device according to claim 10 , further comprising a connection gate trench section which connects the sense gate trench section and the main gate trench section,

wherein the connection gate trench section is formed in at least one of the main well region and the sense well region.