Semiconductor device

1. A semiconductor device comprising:

a silicon carbide layer having a first plane and a second plane facing the first plane;

a first silicon carbide region of a first conductivity type provided in the silicon carbide layer;

a second silicon carbide region of a second conductivity type provided between the first silicon carbide region and the first plane;

a third silicon carbide region of the second conductivity type provided between the first silicon carbide region and the first plane, the third silicon carbide region extending in a first direction parallel to the first plane, the third silicon carbide region being connected to the second silicon carbide region, and the third silicon carbide region having a first width in a second direction, the second direction being parallel to the first plane and perpendicular to the first direction, the first width being narrower than a second width of the second silicon carbide region in the second direction;

a first electrode provided on a side of the first plane of the silicon carbide layer and the first electrode being in contact with the first silicon carbide region;

a second electrode provided on a side of the second plane of the silicon carbide layer; and

a metal silicide layer provided between the first electrode and the second silicon carbide region, the metal silicide layer having a portion being in contact with the first plane, and a shape of the portion being an octagon.

2. The semiconductor device according to claim 1 , wherein at least one side among eight sides of the octagon is parallel to the first direction.

3. The semiconductor device according to claim 1 , further comprising a fourth silicon carbide region of the second conductive type provided between the second silicon carbide region and the metal silicide layer, and the fourth silicon carbide region having a second conductive type impurity concentration higher than a second conductive type impurity concentration of the second silicon carbide region.

4. The semiconductor device according to claim 1 , wherein the metal silicide layer contains nickel silicide or titanium silicide.

5. The semiconductor device according to claim 1 , wherein the first conductivity type is an n type and the second conductivity type is a p type.

6. The semiconductor device according to claim 1 , further comprising a fifth silicon carbide region of the first conductivity type provided between the first silicon carbide region and the second plane, and the fifth silicon carbide region having a first conductivity type impurity concentration higher than a first conductivity type impurity concentration of the first silicon carbide region.

7. The semiconductor device according to claim 1 , wherein a first conductivity type impurity concentration of the first silicon carbide region is 1×10 14 cm −3 or higher and 2×10 16 cm −3 or lower.

8. The semiconductor device according to claim 1 , wherein a second conductivity type impurity concentration of the second silicon carbide region is 1×10 14 cm −3 or higher and 5×10 18 cm −3 or lower.

9. The semiconductor device according to claim 1 , wherein a second conductivity type impurity concentration of the third silicon carbide region is 5×10 16 cm −3 or higher and 5×10 18 cm −3 or lower.

10. The semiconductor device according to claim 1 , wherein a second conductivity type impurity concentration of the fourth silicon carbide region is 1×10 19 cm −3 or higher and 1×10 21 cm −3 or lower.