Silicon carbide semiconductor device

1. A silicon carbide semiconductor device, comprising:

a drift layer, disposed on a substrate, the drift layer has a first conductivity type and an upper surface, and the drift layer comprises an active region;

a first doped region, disposed in the active region adjoining the upper surface, the first doped region has a second conductivity type opposite the first conductivity type and forms a plurality of first p-n junctions and a plurality of JFET regions with the drift layer, the first doped region comprises a plurality of first leg portions, a plurality of body portions, and a plurality of first arm portions, the plurality of first arm portions are extending along a first direction and connecting at least two of the first leg portions, the plurality of first leg portions are extending along a second direction, and the plurality of body portions connect at least two of the first leg portions;

a second doped region, disposed in the first doped region, the second doped region has the first conductivity type and forms a plurality of second p-n junctions with the first doped region, a plurality of channel regions are defined between the first p-n junctions and the second p-n junctions along the upper surface, the second doped region comprises a plurality of second leg portions, a plurality of source portions, and a plurality of second arm portions, the plurality of second leg portions are extending along the second direction, the plurality of source portions are arranged in the body portions and connecting at least two of the second leg portions, and the plurality of second arm portions are extending along the first direction and connecting at least two of the second leg portions;

a plurality of third doped regions, disposed in the body portions, the plurality of third doped regions have the second conductivity type;

a gate insulator, disposed on the upper surface, and the gate insulator extending over the plurality of JFET regions, the channel regions, and part of the second doped region;

a gate electrode, contacting the gate insulator; and

a source electrode, contacting the source portions and the third doped regions,

wherein a channel width density of the active region is higher than 0.2 μm −1 .

2. The silicon carbide semiconductor device of claim 1 , wherein each of the first leg portions is connected to the plurality of body portions only on one side and connected to the plurality of first arm portions only on the other side.

3. The silicon carbide semiconductor device of claim 1 , wherein the third doped regions are disposed adjacent to the source portions in each of the body portions.

4. The silicon carbide semiconductor device of claim 1 , wherein the third doped regions comprise a plurality of sub-regions in some of the body portions, and the sub-regions are separated to each other.

5. The silicon carbide semiconductor device of claim 1 , wherein the third doped regions have a plurality of sizes, and the third doped regions are adjacent to the source portions in some of the body portions.

6. The silicon carbide semiconductor device of claim 1 , wherein the opposite sides of the first arm portions connecting to the same first leg portions are aligned to a same baseline.

7. The silicon carbide semiconductor device of claim 1 , wherein the gate electrode is not contacting the gate insulator above a part of the JFET regions.

8. The silicon carbide semiconductor device of claim 1 , wherein the drift layer further comprises an upper portion and a lower portion, and the upper portion has a doping concentration higher than a doping concentration of the lower portion.

9. The silicon carbide semiconductor device of claim 1 , wherein the first doped region has a first maximum depth in the drift layer, and the first maximum depth is equal to or larger than half of a thickness of the drift layer.

10. The silicon carbide semiconductor device of claim 9 , wherein the third doped regions have a second maximum depth larger than the first maximum depth.

11. The silicon carbide semiconductor device of claim 1 , wherein a doping concentration of the first doped region close to the upper surface is lower than other portion of the first doped region.

12. The silicon carbide semiconductor device of claim 1 , wherein the substrate has the first conductivity type and the silicon carbide semiconductor device is arranged as a metal oxide semiconductor field effect transistor (MOSFET).

13. The silicon carbide semiconductor device of claim 1 , wherein the substrate has the second conductivity type and the silicon carbide semiconductor device is arranged as an insulated gate bipolar transistor (IGBT).