High electron mobility semiconductor device and method therefor
In one embodiment, Group III-nitride materials are used to form a semiconductor device. A fin structure is formed in the Group III-nitride material, and a gate structure, source electrodes and drain electrodes are formed in spaced relationship to the fin structure. The fin structure provides both polar and semi-polar 2DEG regions. In one embodiment, the gate structure is configured to control current flow in the polar 2DEG region. Shield conductor layers are included above the gate structure and in spaced relationship with drain regions of the semiconductor device.
1. A semiconductor device structure comprising:
a substrate of a first material type, the substrate having a first major surface and a second major surface;
a first semiconductor region of a second material type on the first major surface of the substrate;
a first trench extending into the first semiconductor region, the first trench having sidewalls and a bottom surface;
a second semiconductor region of a third material type on the first semiconductor region and within the first trench, wherein the second semiconductor region is configured to form a 2DEG region that is semi-polar proximate to the sidewalls of the first trench and polar proximate to the bottom surface of the first trench;
a control electrode within the first trench and configured to control at least a horizontal portion of the 2DEG region;
a shield conductor layer within the trench and above the control electrode and separated from the control electrode by an insulating layer; and
a first current carrying electrode electrically coupled to 2DEG region.
2. The structure of claim 1 , wherein the first current carrying electrode is along a <0001> crystal plane.
3. The structure of claim 2 , wherein the first current carrying electrode is within the first trench.
4. The structure of claim 3 , wherein the first current carrying electrode further extends through the first semiconductor region and to the substrate.
5. The structure of claim 1 , wherein:
the first current carrying electrode is connected to the shield conductor layer outside of the first trench;
the shield conductor layer includes a portion within the trench that is separated from the sidewalls of the trench by an insulating layer that increases in thickness in a direction from the bottom surface of the trench towards a top portion of the trench; and
the structure further comprises a second current carrying electrode electrically coupled to the first and second semiconductor regions outside of the trench.
6. The structure of claim 1 further comprising a third semiconductor region of a fourth material type between the first semiconductor region and the second semiconductor region, wherein:
the second material type comprises AlGaN;
the third material type comprises AlGaN;
the fourth material type comprises GaN; and
wherein the second semiconductor region forms the 2DEG region with the third semiconductor region.
7. The structure of claim 1 , wherein the control electrode comprises a stepped structure configured as a field plate.
8. The structure of claim 1 , wherein the shield conductor layer comprises one or more of a stepped structure, a sloped structure, and a block structure.
9. A method of forming a semiconductor device comprising:
providing a substrate of a first material type, the substrate having a first major surface and a second major surface, a first semiconductor region of a second material type on the first major surface of the substrate, a first trench extending into the first semiconductor region, the first trench having sidewalls and a bottom surface, and a second semiconductor region of a third material type on the first semiconductor region and with the first trench, wherein the second semiconductor region is configured to form a 2DEG region that is semi-polar proximate to the sidewalls of the first trench and polar proximate to the bottom surface of the first trench;
forming a control electrode within the first trench and configured to control at least a lateral portion of the 2DEG region;
forming a shield conductor layer within the trench and above the control electrode and separated from the control electrode by a insulating layer; and
forming a first current carrying electrode electrically coupled to 2DEG region.
10. A semiconductor structure comprising:
a substrate of a first material type, the substrate having a first surface and a second surface;
a first semiconductor region of a first material on the first surface of the substrate and including a first fin structure, the first fin structure comprising:
a generally horizontal first top surface;
a recessed surface portion adjacent the first top surface; and
first sidewall surfaces extending between the recessed surface portion and the first top surface, the first sidewall surfaces being sloped so that a base portion of the first fin structure is wider than the first top surface;
a second semiconductor region of a second material on the first semiconductor region, wherein the second semiconductor region is configured to form a 2DEG region that is semi-polar proximate to the first sidewall surfaces and polar proximate to the recessed surface portion;
a gate conductor overlying at least part of the recessed surface portion; and
a first current carrying electrode electrically coupled to the second semiconductor region along at least the first top surface.
11. The structure of claim 10 further comprising a shield conductor above and insulated from the gate conductor, and wherein the first current carrying electrode and the shield conductor are electrically coupled together.
12. The structure of claim 10 , wherein:
the first material is a Group III-nitride material; and
the second material is a Group III-nitride material.
13. The structure of claim 12 , wherein the first semiconductor region comprises a GaN channel region and the second semiconductor region comprises an AlGaN barrier region.
14. The structure of claim 12 , further comprising a third semiconductor region of a Group III-nitride material type between the first and second semiconductor regions, wherein the first semiconductor region comprises a buffer region, the third semiconductor region comprises a GaN channel region, and the second semiconductor region comprises an AlGaN barrier region, and wherein the first current carrying electrode contacts the AlGaN barrier region, and wherein the substrate comprises a semiconductor material.
15. The structure of claim 10 further comprising:
a second current carrying electrode electrically coupled to the second semiconductor region at least along the first top surface and spaced apart from the first current carrying electrode, wherein:
the gate conductor further overlies the first top surface between the first and second current carrying electrodes; and
the shield conductor laterally extends between the gate conductor and the first current carrying electrode and further laterally extends proximate to the second current carrying electrode.
16. The structure of claim 10 , wherein the first semiconductor region includes a second fin structure, the second fin structure having a generally horizontal second top surface and second sidewall surfaces extending between second top surface and the recessed surface portion; and
a second current carrying electrode electrically coupled to the second semiconductor region along at least the second top surface.
17. The structure of claim 10 further comprising a second current carrying electrode on the second surface of the substrate.
18. The structure of claim 10 , wherein:
the first sidewall surfaces are {01 1 2} family R-plane surfaces; and
the first top surface is along a <0001> crystal plane.
19. The structure of claim 1 , wherein:
the gate conductor overlies part of the first fin structure; and
the first current carrying electrode overlies part of the recessed surface portion.
20. The structure of claim 10 , wherein:
the gate conductor overlies part of the first sidewall surfaces and part of the first top surface; and
the first current carrying electrode overlies another part of the first sidewall surfaces and another part the recessed surface portion.