Methods for forming FinFETS having a capping layer for reducing punch through leakage

1. A semiconductor structure comprising:

a semiconductor substrate;

a fin disposed on the substrate having an upper portion and a lower portion;

a capping layer disposed on a lower surface portion of the fin, the capping layer not disposed on an upper surface portion of the fin;

an isolation fill disposed over the capping layer;

a gate disposed over the upper surface portion of the fin, the gate not disposed below the upper portion of the fin; and

wherein the capping layer and the lower portion of the fin define an interface dipole layer barrier below the upper portion of the fin and the gate, a portion of the capping layer operable to provide an increased negative charge or an increased positive charge adjacent to the lower portion of the fin, to reduce punch-through leakage compared to a fin without the capping layer.

2. The semiconductor structure of claim 1 wherein the gate is disposed on the upper surface portion of the fin.

3. The semiconductor structure of claim 1 wherein the fin comprises a plurality of fins, and the capping layer comprises a first capping layer disposed over some of lower portions of the fins, the first capping layer not disposed on the upper surface portions of the fins, and a second capping layer disposed over other of lower portions of the fins, the second capping layer not disposed on the upper surface portions of the fins, and wherein the first capping layer being different from the second capping layer.

4. The semiconductor structure of claim 3 wherein the first capping layer comprises a negative charge, and the second capping layer comprises a positive charge.

5. The semiconductor structure of claim 4 wherein the first capping layer comprises strontium oxide, lanthanum oxide, lutetium oxide, yttrium oxide, or germanium oxide, and the second capping layer comprises aluminum oxide, titanium dioxide, zirconium dioxide, hafnium oxide, or magnesium oxide.

6. The semiconductor structure of claim 4 wherein the plurality of gates is disposed on the plurality of upper surface portions of the fins.

7. A semiconductor structure comprising:

a semiconductor substrate and a first plurality of fins and a second plurality of fins disposed on the semiconductor substrate;

a first capping layer disposed on lower surface portions of the first plurality of fins, the first capping layer not disposed on upper surface portion of the first plurality of fins, and a first isolation fill disposed over the first capping layer;

a second capping layer disposed on lower surface portions of the second plurality of fins, the second capping layer not disposed on upper surface portions of the second plurality of fins, and a second isolation fill disposed over the second capping layer, the second capping layer being different from the first capping layer;

a plurality of gates disposed on the upper surface portions of the first plurality of fins and the second plurality of fins, the gates not disposed below the upper portions of the plurality of fins; and

wherein the first and second capping layers and lower portions of the first and second plurality of fins define interface dipole layer barriers below the upper portions of the first and second plurality of fins and the gates, portions of the first and second capping layers operable to provide increased negative charges or increased positive charges adjacent to the lower portions of the first and second plurality of fins, to reduce punch-through leakage compared to fins not having the capping layers.

8. The structure of claim 7 wherein the first capping layer is over an NFET region in the substrate.

9. The structure of claim 8 wherein the second capping layer is over a PFET region in the substrate.

10. The structure of claim 7 wherein the first capping layer comprises a negative charge, and the second capping layer comprises a positive charge.

11. The structure of claim 7 wherein the first capping layer and the second capping layer comprise an oxide.

12. The structure of claim 7 wherein the first capping layer comprises strontium oxide, lanthanum oxide, lutetium oxide, yttrium oxide, or germanium oxide, and the second capping layer comprises aluminum oxide, titanium dioxide, zirconium dioxide, hafnium oxide, or magnesium oxide.

13. The structure of claim 7 wherein the first and the second plurality of gates are disposed the on upper surface portions of the fins.