SEMICONDUCTOR DEVICE AND METHOD FOR MANUFACTURING THE SAME

Abstract

A semiconductor device includes a first electrode, a first semiconductor layer of a first conductivity type on the first electrode, a first pillar of a second conductivity type on the first semiconductor layer, the first pillar having a first average concentration of impurities, a second pillar of the first conductivity type on the first semiconductor layer, and including a first layer having a second average concentration of impurities lower than the first average concentration, and a second layer having a third average concentration of impurities higher than the first average concentration, a second semiconductor layer of the second conductivity type on the second pillar, a third semiconductor layer of the first conductivity type on the second semiconductor layer, a second electrode connected to the first pillar and the third semiconductor layer, a third electrode, and an insulating film disposed between the second semiconductor layer and the third electrode.

Description

Claims

1. A semiconductor device comprising: a first electrode;a first semiconductor layer of a first conductivity type provided on the first electrode;a first pillar of a second conductivity type provided on the first semiconductor layer, the first pillar having a first average concentration of impurities of the second conductivity type;a second pillar of the first conductivity type provided on the first semiconductor layer, and including a first layer having a second average concentration of impurities of the first conductivity type, that is lower than the first average concentration, and a second layer having a third average concentration of impurities of the first conductivity type, that is higher than the first average concentration;a second semiconductor layer of the second conductivity type provided on the second pillar;a third semiconductor layer of the first conductivity type provided on the second semiconductor layer;a second electrode connected to the first pillar and the third semiconductor layer;a third electrode; andan insulating film disposed between the second semiconductor layer and the third electrode.

2. The semiconductor device according to claim 1, wherein the first semiconductor layer, the second semiconductor layer, the third semiconductor layer, the first layer, the second layer, and the first pillar contain silicon carbide.

3. The semiconductor device according to claim 1, wherein a difference between a maximum value and a minimum value of the impurity concentrations in the first layer is smaller than a difference between a maximum value and a minimum value of the impurity concentrations in the second layer.

4. The semiconductor device according to claim 3, wherein a difference between a maximum value and a minimum value of the impurity concentrations in the first pillar is greater than the difference between the maximum value and the minimum value of the impurity concentrations in the first layer, and smaller than the difference between the maximum value and the minimum value of the impurity concentrations in the second layer.

5. The semiconductor device according to claim 1, wherein the second pillar includes alternating layers of the first layer and the second layer along a first direction from the first electrode to the second electrode.

6. The semiconductor device according to claim 5, wherein the first pillar has a plurality of layers of the second conductivity type along the first direction, each of the layers of the first pillar corresponding to one pair of the first layer and the second layer along the first direction, andin each of the layers of the second pillar, an impurity concentration profile along the first direction has one peak, and in each of the second layers, an impurity concentration profile along the first direction has one peak.

7. The semiconductor device according to claim 5, wherein in the first pillar, an impurity concentration profile along the first direction is constant, andin each of the second layers, an impurity concentration profile along the first direction has one peak.

8. The semiconductor device according to claim 1, wherein the second pillar has no layer having the third average concentration of impurities of the first conductivity type other than the second layer.

9. The semiconductor device according to claim 8, wherein the first layer is in direct contact with the first semiconductor layer and the second layer is in direct contact with the first layer.

10. The semiconductor device according to claim 8, wherein the first layer is in direct contact with the second layer and the second layer is in direct contact with the second semiconductor layer.

11. The semiconductor device according to claim 8, wherein the first layer and the second layers are between two other layers of the second pillar.

12. The semiconductor device according to claim 1, wherein the second pillar includes a third layer having the second average concentration of impurities of the first conductivity type, a fourth layer having the third average concentration of impurities of the first conductivity type, and a fifth layer having the second average concentration of impurities of the first conductivity type, andthe fifth layer is between and in contact with the second layer and the third layer, and has twice the thickness of the thickness of each of the first, second, third, and fourth layers.

13. A method of manufacturing a semiconductor device comprising: injecting impurities of a second conductivity type into a first part of a first semiconductor layer of a first conductivity type, and injecting impurities of the first conductivity type into a second part of the first semiconductor layer, wherein the impurities of the first conductivity type are injected less deeply into the second part than the impurities of the second conductivity type are injected into the first part;forming an epitaxial layer of the first conductivity type on the first semiconductor layer;injecting impurities of the second conductivity type impurity into a third part of the epitaxial layer that is aligned vertically with the first part, and injecting impurities of the first conductivity type into a fourth part of the epitaxial layer that is aligned vertically with the second part, wherein the impurities of the first conductivity type are injected less deeply into the fourth part than the impurities of the second conductivity type are injected into the third part;forming a second semiconductor layer of the second conductivity type above the epitaxial layer;forming a third semiconductor layer of the first conductivity type on the second semiconductor layer;forming an insulating film in contact with the second semiconductor layer;forming a third electrode that is separated from the second semiconductor layer by the insulating film; andforming a first electrode connected to the first semiconductor layer, and forming a second electrode connected to the third part and the third semiconductor layer.

14. The method of claim 13, wherein the impurities of the first conductivity type are injected one-half as deeply into the second part as the impurities of the second conductivity type are injected into the first part, and the impurities of the first conductivity type are injected one-half as deeply into the fourth part as the impurities of the second conductivity type are injected into the third part.

15. The method of claim 13, further comprising: prior to forming the second semiconductor layer, forming a fourth semiconductor layer of the first conductivity type above the epitaxial layer and aligned vertically with the fourth part and forming a fifth semiconductor layer of the second conductivity type above the epitaxial layer and aligned vertically with the third part.

16. The method of claim 14, wherein the third electrode is separated from the fourth semiconductor layer by the insulating film.

17. A method of manufacturing a semiconductor device comprising: injecting impurities of a first conductivity type into a first part of a first semiconductor layer of the first conductivity type;forming a first epitaxial layer of the first conductivity type on the first semiconductor layer;injecting impurities of the first conductivity type impurity into a second part of the first epitaxial layer that is aligned vertically with the first part;forming a hole penetrating the first epitaxial layer and reaching an interior of the first semiconductor layer;forming a second epitaxial layer of a second conductivity type in the hole;forming a second semiconductor layer of the second conductivity type above the first epitaxial layer and the second epitaxial layer;forming a third semiconductor layer of the first conductivity type on the second semiconductor layer;forming an insulating film in contact with the second semiconductor layer;forming a third electrode that is separate from the second semiconductor layer by the insulating film; andforming a first electrode connected to the first semiconductor layer, and forming a second electrode connected to the second epitaxial layer and the third semiconductor layer.

18. The method of claim 17, wherein the impurities of the first conductivity type are injected into the first part and the second part to a depth that is one-half the thickness of the first epitaxial layer.

19. The method of claim 17, further comprising: prior to forming the second semiconductor layer, forming a fourth semiconductor layer of the first conductivity type above the first epitaxial layer and aligned vertically with the second part and forming a fifth semiconductor layer of the second conductivity type above the second epitaxial layer.

20. The method of claim 19, wherein the third electrode is separated from the fourth semiconductor layer by the insulating film.