Silicon carbide semiconductor device and manufacturing method thereof
View Patent ↗A silicon carbide semiconductor device includes a semiconductor substrate containing silicon carbide, a semiconductor layer formed over the semiconductor substrate, and a plurality of well regions formed on a front surface side of a cell forming area set to the semiconductor layer. The device further includes source layers formed on the front surface side lying within the well regions, an outer peripheral insulating film thick in thickness, which is formed over the semiconductor layer in an outer peripheral area surrounding the cell forming area, a gate oxide film formed over the front surface of the semiconductor layer in the cell forming area, and a gate electrode layer formed so as to extend from above the gate oxide film to above the outer peripheral insulating film.
1. A silicon carbide semiconductor device comprising:
a semiconductor substrate comprising silicon carbide, which contains a first conductivity type impurity diffused therein in a high concentration;
a semiconductor layer formed over the semiconductor substrate and containing the first conductivity type impurity diffused therein in a low concentration;
a plurality of well regions formed on a front surface side of a cell forming area set to the semiconductor layer and in which a second conductivity type impurity corresponding to a type opposite to the first conductivity type impurity is diffused;
source layers formed on the front surface side lying within the well regions and each containing the first conductivity type impurity diffused therein in a high concentration;
an outer peripheral insulating film thick in thickness, which is formed over the semiconductor layer in an outer peripheral area surrounding the cell forming area;
a gate oxide film formed over the front surface of the semiconductor layer in the cell forming area; and
a gate electrode layer formed so as to extend from above the gate oxide film to above the outer peripheral insulating film,
wherein each of steplike portions adjacent to the outer peripheral insulating film and thicker than the gate oxide film in thickness is provided at an edge portion of the gate oxide film.
2. The silicon carbide semiconductor device according to claim 1 , wherein the gate oxide film is a thermal oxide film.
3. The silicon carbide semiconductor device according to claim 1 , wherein the first conductivity type is N-type, and the silicon carbide semiconductor device is a vertical nMOS transistor.
4. The silicon carbide semiconductor device according to claim 1 , wherein a thickness of steplike portions of the gate oxide film is less than the thickness of the outer insulating film.
5. The silicon carbide semiconductor device according to claim 1 , wherein gate electrode layer includes a steplike portion conforming to the steplike portion of the gate oxide film.
6. The silicon carbide semiconductor device according to claim 1 , wherein the gate electrode layer extends over a source layer adjacent the outer peripheral area, and wherein the device further comprises a plurality of additional gate electrodes located between respective source layers which are not adjacent the outer peripheral area.
7. The silicon carbide semiconductor device according to claim 6 , further comprising a source electrode pad which is electrically connected to the plurality of source layers.