Semiconductor device
A semiconductor device includes n-type drift layer, n-type current spreading layer having higher impurity concentration than the drift layer, p-type base region provided on top surface, p-type gate-bottom protection region located in the current spreading layer, having first bottom edge portion formed of curved surface, p-type base-bottom embedded region in contact with bottom surface of the base region, having second bottom edge portion formed of curved surface on side surface facing the gate-bottom protection region, being separated from the gate-bottom protection region, and insulated gate electrode structure provided in trench penetrating through the base region to reach the gate-bottom protection region. Bottom surface of the base-bottom embedded region is deeper than bottom surface of the gate-bottom protection region, and minimum value of curvature radius of the first bottom edge portion is larger than minimum value of curvature radius of the second bottom edge portion.
1. A semiconductor device comprising:
a drift layer of a first conductivity type made of a hexagonal semiconductor having a wider bandgap than silicon;
a current spreading layer of the first conductivity type disposed on a top surface of the drift layer, having a higher impurity concentration than the drift layer;
a base region of a second conductivity type disposed on a top surface of the current spreading layer;
a gate-bottom protection region of the second conductivity type located in the current spreading layer, having a first bottom edge portion formed of a curved surface;
a base-bottom embedded region of the second conductivity type in contact with a bottom surface of the base region while being separated from the gate-bottom protection region in the current spreading layer, the base-bottom embedded region having a second bottom edge portion formed of a curved surface on a side surface facing the gate-bottom protection region; and
an insulated-gate electrode structure provided in a trench penetrating the base region to reach the gate-bottom protection region,
wherein in a cross section perpendicularly cut to an extending direction of the trench,
a bottom surface of the base-bottom embedded region is placed deeper than a bottom surface of the gate-bottom protection region, and
a minimum value of a curvature radius of the first bottom edge portion is larger than a minimum value of a curvature radius of the second bottom edge portion.
2. The semiconductor device of claim 1 , wherein the gate-bottom protection region has a higher impurity concentration than the base-bottom embedded region.
3. The semiconductor device of claim 1 , wherein the gate-bottom protection region has an impurity concentration of 3×10 18 cm −3 or more and less than 1×10 19 cm −3 .
4. The semiconductor device of claim 1 , wherein the base-bottom embedded region has an impurity concentration of 1×10 17 cm −3 or more and less than 3×10 18 cm −3 .
5. The semiconductor device of claim 1 , wherein the gate-bottom protection region has a top edge portion formed of a curved surface, and a minimum value of a curvature radius of the top edge portion is larger than the minimum value of the curvature radius of the second bottom edge portion.
6. The semiconductor device of claim 1 , further comprising a local current spreading layer of the first conductivity type in contact with a bottom surface of the base-bottom embedded region, having a higher impurity concentration than the current spreading layer.
7. The semiconductor device of claim 1 , further comprising a guard ring of the second conductivity type disposed around an active area where the insulated-gate electrode structure is provided, a bottom surface of the guard ring being located at the same depth level as the bottom surface of the base-bottom embedded region on the drift layer, and the guard ring has the same impurity concentration as the base-bottom embedded region.
8. The semiconductor device of claim 1 , wherein the hexagonal semiconductor is silicon carbide.