CMOS compatible isolation leakage improvements in gallium nitride transistors

1. An integrated circuit structure, comprising:

a silicon substrate;

a III-nitride (III-N) substrate over the silicon substrate;

a first III-N transistor and a second III-N transistor on the III-N substrate; and

an insulator structure formed in the III-N substrate between the first III-N transistor and the second III-N transistor, wherein the insulator structure comprises one of:

a shallow trench filled with an oxide, nitride or low-K dielectric, wherein the oxide, nitride or low-K dielectric is coplanar with a top of metal contacts on the respective source and drain regions of the first III-N transistor and the second III-N transistor; or

a first gap adjacent to the first III-N transistor and a second gap adjacent to the second III-N transistor, wherein the first gap is in contact with a source and drain region of the first III-N transistor and the second gap is in contact with a source drain region of the second III-N transistor, where the first gap and the second gap are separated by a dielectric material.

2. The integrated circuit structure of claim 1 , wherein the first gap and the second gap are filled with at least one of air, a gas, a dielectric, and a liquid.

3. The integrated circuit structure of claim 1 , wherein the first gap and the second gap have respective top portions and bottom portions, wherein the top portions are located in an interlayer dielectric (ILD) at approximately ½ a height of the respective source and drain regions of the first III-N transistor and the second III-N transistor, and the bottom portions are located in the III-N substrate at approximately one half a depth of the III-N substrate such that the bottom portions do not contact the silicon substrate.

4. The integrated circuit structure of claim 1 , wherein the first gap and the second gap and are formed as an opening with borders defined by an interlayer dielectric (ILD) along a top portion and along a first side bordered by the III-N substrate along bottom portions; and bordered by both the source and drain regions and the III-N substrate along a second side.

5. The integrated circuit structure of claim 1 , wherein the first III-N transistor comprises source and drain regions, a polarization layer on the III-N substrate between the source and drain regions, and a gate electrode over the polarization layer.

6. The integrated circuit structure of claim 1 , wherein the second III-N transistor comprises source and drain regions, a polarization layer on the III-N substrate between the source and drain regions, and a gate electrode over the polarization layer.

7. The integrated circuit structure of claim 1 , wherein the first III-N transistor and the second III-N transistor comprise gallium nitride (GaN) transistors.

8. The integrated circuit structure of claim 1 , wherein the shallow trench is filled with a bi-layer stack comprising a high-K dielectric liner formed on the sidewalls and a bottom of the shallow trench, and the oxide, nitride or low-K dielectric formed on the high-K dielectric and filling a remainder of the shallow trench.

9. The integrated circuit structure of claim 8 , wherein the high-K dielectric liner comprises one of aluminum oxide and hafnium oxide.

10. The integrated circuit structure of claim 8 , wherein the high-K dielectric liner is approximately 2 nm in thickness.

11. The integrated circuit structure of claim 1 , wherein the shallow trench extends into the III-N substrate to a depth of approximately 200 nm to 500 nm.

12. The integrated circuit structure of claim 1 , wherein sides of the respective source and drain regions of the first III-N transistor and the second III-N transistor form sidewalls of the shallow trench.

13. The integrated circuit structure of claim 1 , wherein a width of the shallow trench is approximately 300 nm to several microns.