Silicon carbide semiconductor device and manufacturing method of silicon carbide semiconductor device
A silicon carbide semiconductor device includes a substrate, a drift layer disposed above the substrate, a base region disposed above the drift layer, a source region disposed above the base region, a gate trench formed deeper than the base region from a surface of the source region, a gate insulating film covering an inner wall surface of the gate trench, a gate electrode disposed on the gate insulating film, an interlayer insulating film covering the gate electrode and the gate insulating film and having a contact hole, a source electrode brought in ohmic contact with the source region through the contact hole, and a drain electrode disposed to a rear surface of the substrate. The source region has a lower impurity concentration on a side close to the base region than on a surface side brought in ohmic contact with the source region.
1. A silicon carbide semiconductor device including an inverted semiconductor element, comprising:
a substrate made of silicon carbide of a first or second conductivity type;
a drift layer disposed above the substrate, made of silicon carbide of the first conductivity type, and having an impurity concentration lower than an impurity concentration of the substrate;
a base region disposed above the drift layer, and made of silicon carbide of the second conductivity type;
a source region disposed above the base region, made of silicon carbide of the first conductivity type, and having an impurity concentration higher than the impurity concentration of the drift layer;
a plurality of trench gate structures aligned in stripes with one direction as a longitudinal direction, and each including a gate trench formed deeper than the base region from a surface of the source region, a gate insulating film covering an inner wall surface of the gate trench, and a gate electrode disposed on the gate insulating film;
an interlayer insulating film covering the gate electrode and the gate insulating film and having a contact hole;
a source electrode brought in ohmic contact with the source region through the contact hole;
a drain electrode disposed to a rear surface of the substrate; and
a non-doped layer having a carrier concentration of 5.0×10 15 cm −3 or less, and provided between the base region and the source region, wherein
the source region has a lower impurity concentration on a side close to the base region than on a surface side brought in ohmic contact with the source region.
2. The silicon carbide semiconductor device according to claim 1 , wherein the source region includes a first source region located close to the base region and a second source region brought in ohmic contact with the source electrode.
3. The silicon carbide semiconductor device according to claim 2 , wherein the second source region has a thickness of 0.1 μm or more and has a second conductivity type impurity concentration of 1.0×10 18 to 5.0×10 19 cm −3 .
4. The silicon carbide semiconductor device according to claim 2 , wherein the first source region has a thickness of 0.2 to 0.5 μm and has an impurity concentration of 2.0×10 16 to 1.0×10 17 cm −3 .
5. The silicon carbide semiconductor device according to claim 1 , wherein the non-doped layer has a thickness of 0.05 to 0.2 μm.
6. The silicon carbide semiconductor device according to claim 1 , wherein a total film thickness of the non-doped layer and the source region is 0.8 μm or less.