Semiconductor device and method of manufacturing semiconductor device

1. A semiconductor device, comprising:

a first drain region of a first conductivity type and made primarily of silicon carbide, in a substrate;

a drift layer of the first conductivity type above the first drain region;

a channel region of a second conductivity type above the drift layer;

a first source region of the first conductivity type in a portion of an upper surface of the channel region;

a source electrode above the first source region;

a second drain region of the first conductivity type disposed in a portion of the upper part of the channel region and having a pattern connected to the first source region;

a second source region of the first conductivity type in a portion of the upper surface of the channel region and separated from the second drain region;

a first floating electrode connected to the second source region and the channel region;

a first gate electrode controlling a surface potential of a path for current that flows from the first source region in the channel region to the drift layer; and

a second gate electrode that is connected to the first gate electrode and that controls a surface potential of the channel region between the second drain region and the second source region.

2. The semiconductor device according to claim 1 , further comprising:

a first ohmic contact layer disposed between the first source region and the source electrode and respectively contacting the first source region and the source electrode; and

a first potential barrier layer contacting the channel region and preventing injection of majority carriers into the channel region,

wherein the source electrode electrically connects the first ohmic contact layer and the first potential barrier layer.

3. The semiconductor device according to claim 2 , further comprising:

a base region of the second conductivity type disposed between the drift layer and the channel region and having a higher impurity concentration than the channel region.

4. The semiconductor device according to claim 2 , wherein a plurality of openings penetrating the first source region and exposing the channel region are discretely arranged along a lengthwise direction of the first source region, and the first potential barrier layer is disposed in each of the plurality of openings.

5. The semiconductor device according to claim 2 , further comprising:

an inverted region of the first conductivity type sandwiching the channel region; and

a JFET region between the drift layer and a bottom surface of the inverted region.

6. The semiconductor device according to claim 2 , wherein the first potential barrier layer is a metal that forms a Schottky junction with the channel region.

7. The semiconductor device according to claim 2 , wherein the first potential barrier layer is a semiconductor layer that forms a heterojunction.

8. The semiconductor device according to claim 7 , wherein the first potential barrier layer is a polycrystalline silicon layer.

9. The semiconductor device according to claim 6 , wherein a barrier height of the Schottky junction to holes is 0.5 eV to 2.26 eV.

10. The semiconductor device according to claim 9 , wherein the barrier height is greater than or equal to 1 eV.

11. The semiconductor device according to claim 1 , further comprising:

a second ohmic contact layer disposed above the channel region and contacting the channel region;

an inverted region connecting together the channel region and the first source region;

a second potential barrier layer forming a Schottky junction with the inverted region; and

a second floating electrode contacting the second ohmic contact layer and the second potential barrier layer.

12. The semiconductor device according to claim 1 , wherein the first gate electrode is a planar-gate electrode.

13. The semiconductor device according to claim 1 , wherein the first gate electrode is a trench-gate electrode.

14. The semiconductor device according to claim 12 , wherein the second gate electrode is a planar-gate electrode.

15. The semiconductor device according to claim 1 , further comprising:

a Schottky diode connected in parallel to the semiconductor device within an active portion in which the semiconductor device is embedded.

16. A method of manufacturing a semiconductor device, comprising:

forming, on a first drain region made of silicon carbide, a drift layer of a first conductivity type and a lower concentration of impurities than the first drain region;

forming a channel region of a second conductivity type above the drift layer;

forming, in a portion of an upper surface of the channel region, a first source region of the first conductivity type, a second drain region of the first conductivity type to be connected to the first source region, and a second source region of the first conductivity type separated from the second drain region;

forming a gate insulating film above the channel region;

forming, above the gate insulating film, a first gate electrode controlling a surface potential of a path for current that flows from the first source region in the channel region to the drift layer, and a second gate electrode connected to the first gate electrode and controlling a surface potential of the channel region between the second drain region and the second source region;

forming a source electrode on the first source region; and

forming a first floating electrode separated from the source electrode and connected to the second source region and the channel region.

17. The method of manufacturing the semiconductor device according to claim 16 , further comprising:

forming a first ohmic contact layer between and contacting the first source region and the source electrode; and

forming a first potential barrier layer contacting the channel region.