Silicon carbide semiconductor device including conductivity layer in trench
First Claim
1. A silicon carbide semiconductor device comprising:
- a silicon carbide substrate that is of either a first conductivity type, or a second conductivity type that is opposite the first conductivity type;
a drift layer that is disposed on the substrate, and made of a first conductivity type silicon carbide lower in impurity concentration than the substrate;
a base region that is disposed on the drift layer, and made of a second conductivity type silicon carbide;
a source region that is disposed on the base region, and made of a first conductivity type silicon carbide higher in impurity concentration than the drift layer;
a contact region that is connected to the base region, and made of a second conductivity type silicon carbide higher in impurity concentration than the base region;
a trench that extends to a position deeper than the base region from a surface of the source region;
a second conductivity type layer that is disposed in a bottom of the trench, and is made of a second conductivity type silicon carbide;
a gate insulating film that is disposed on an inner wall surface of the trench on the second conductivity type layer;
a gate electrode that is disposed on the gate insulating film within the trench;
a source electrode that is electrically connected to the base region through the source region and the contact region; and
a drain electrode that is disposed on a rear side of the substrate,wherein the silicon carbide semiconductor device has an inversion type semiconductor switching element with a trench gate structure that forms an inversion type channel region on a surface portion of the base region located on a side surface of the trench through control of an application voltage to the gate electrode, and allows a current to flow between the source electrode and the drain electrode through the source region and the drift layer;
wherein the trench defines a longitudinal direction in one direction, and the bottom of the trench has a predetermined width;
wherein the gate insulating film contacts a bottom surface of the trench;
wherein the second conductivity type layer disposed in the bottom of the trench includes a first corner portion and a second corner portion;
wherein the first corner portion and the second corner portion of the second conductivity type layer are disposed at opposite corners of the bottom of the trench and separated from each other by the gate insulating film, which contacts the bottom surface of the trench, in a width direction of the trench in a cross-section taken along a depth direction and the width direction of the trench; and
wherein each of the first corner portion and the second corner portion has a triangular round shape in the cross-section taken along the depth direction and the width direction of the trench, the triangular round shape being defined by two sides that contact the side surface of the trench and the bottom surface of the trench and one side that contacts the gate insulating film.
1 Assignment
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Accused Products
Abstract
In a silicon carbide semiconductor device, a p-type SiC layer is disposed in a corner of a bottom of a trench. Thus, even if an electric field is applied between a drain and a gate when a MOSFET is turned off, a depletion layer in a pn junction between the p-type SiC layer and an n− type drift layer greatly extends toward the n− type drift layer, and a high voltage caused by an influence of a drain voltage hardly enters a gate insulating film. Hence, an electric field concentration within the gate insulating film can be reduced, and the gate insulating film can be restricted from being broken. In this case, although the p-type SiC layer may be in a floating state, the p-type SiC layer is formed in only the corner of the bottom of the trench. Thus, the deterioration of the switching characteristic is relatively low.
15 Citations
10 Claims
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1. A silicon carbide semiconductor device comprising:
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a silicon carbide substrate that is of either a first conductivity type, or a second conductivity type that is opposite the first conductivity type; a drift layer that is disposed on the substrate, and made of a first conductivity type silicon carbide lower in impurity concentration than the substrate; a base region that is disposed on the drift layer, and made of a second conductivity type silicon carbide; a source region that is disposed on the base region, and made of a first conductivity type silicon carbide higher in impurity concentration than the drift layer; a contact region that is connected to the base region, and made of a second conductivity type silicon carbide higher in impurity concentration than the base region; a trench that extends to a position deeper than the base region from a surface of the source region; a second conductivity type layer that is disposed in a bottom of the trench, and is made of a second conductivity type silicon carbide; a gate insulating film that is disposed on an inner wall surface of the trench on the second conductivity type layer; a gate electrode that is disposed on the gate insulating film within the trench; a source electrode that is electrically connected to the base region through the source region and the contact region; and a drain electrode that is disposed on a rear side of the substrate, wherein the silicon carbide semiconductor device has an inversion type semiconductor switching element with a trench gate structure that forms an inversion type channel region on a surface portion of the base region located on a side surface of the trench through control of an application voltage to the gate electrode, and allows a current to flow between the source electrode and the drain electrode through the source region and the drift layer; wherein the trench defines a longitudinal direction in one direction, and the bottom of the trench has a predetermined width; wherein the gate insulating film contacts a bottom surface of the trench; wherein the second conductivity type layer disposed in the bottom of the trench includes a first corner portion and a second corner portion; wherein the first corner portion and the second corner portion of the second conductivity type layer are disposed at opposite corners of the bottom of the trench and separated from each other by the gate insulating film, which contacts the bottom surface of the trench, in a width direction of the trench in a cross-section taken along a depth direction and the width direction of the trench; and wherein each of the first corner portion and the second corner portion has a triangular round shape in the cross-section taken along the depth direction and the width direction of the trench, the triangular round shape being defined by two sides that contact the side surface of the trench and the bottom surface of the trench and one side that contacts the gate insulating film. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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Specification