Semiconductor structures with backside gate contacts

1. A semiconductor structure comprising:

a substrate having a first side and a second side opposite the first side;

a buried power rail at least partially disposed in the substrate;

a gate for at least one transistor device disposed above the first side of the substrate; and

a gate tie-down contact connecting the gate to the buried power rail from the second side of the substrate.

2. The semiconductor structure of claim 1 , further comprising one or more source/drain regions of the at least one transistor device disposed above the first side of the substrate and one or more dielectric pillars disposed in the substrate below the one or more source/drain regions, wherein the one or more dielectric pillars separate the gate tie-down contact from the one or more source/drain regions.

3. The semiconductor structure of claim 1 , wherein the at least one transistor device comprises a nanosheet field-effect transistor device, and further comprising two or more nanosheet channel layers for the nanosheet field-effect transistor device disposed over the first side of the substrate.

4. The semiconductor structure of claim 3 , wherein the gate tie-down contact connects to a portion of the gate disposed between the two or more nanosheet channel layers and the first side of the substrate.

5. The semiconductor structure of claim 1 , wherein the at least one transistor device comprises a fin field-effect transistor device, and further comprising two or more fin channels disposed over the first side of the substrate.

6. The semiconductor structure of claim 5 , wherein the fin field-effect transistor device comprises a gate-all-around fin field-effect transistor device, and wherein the gate tie-down contact connects to a portion of the gate disposed between the two or more fin channels and the first side of the substrate.

7. The semiconductor structure of claim 5 , wherein the fin field-effect transistor device comprises a non-gate-all-around fin field-effect transistor device, and wherein the gate tie-down contact connects to a portion of the gate disposed to a lateral side of the two or more fin channels.

8. The semiconductor structure of claim 1 , wherein the at least one transistor device comprises a stacked transistor device comprising two or more channel layers disposed over the first side of the substrate, the two or more channel layers comprising at least a first channel layer for a lower transistor of the stacked transistor device and at least a second channel layer for an upper transistor of the stacked transistor device.

9. The semiconductor structure of claim 8 , wherein the gate tie-down contact connects to a portion of the gate that surrounds both the first channel layer and the second channel layer.

10. The semiconductor structure of claim 9 , wherein the portion of the gate surrounding both the first channel layer and the second channel layer is disposed between the first channel layer and the first side of the substrate.

11. The semiconductor structure of claim 8 , wherein the first channel layer is separated from the second channel layer by a dielectric separation layer.

12. The semiconductor structure of claim 11 , wherein the gate tie-down contact connects to a portion of the gate that surrounds the first channel layer but not the second channel layer.

13. The semiconductor structure of claim 12 , wherein the portion of the gate that surrounds the first channel layer but not the second channel layer is disposed between the first channel layer and the first side of the substrate.

14. The semiconductor structure of claim 11 , wherein the gate tie-down contact connects to a portion of the gate that surrounds the second channel layer but not the first channel layer.

15. The semiconductor structure of claim 14 , wherein the portion of the gate that surrounds the second channel layer but not the first channel layer is disposed to a lateral side of the first channel layer.

16. An integrated circuit comprising the semiconductor structure of claim 1 .

17. A semiconductor structure comprising:

a substrate having a first side and a second side opposite the first side;

one or more source/drain regions disposed over the first side of the substrate;

a gate for at least one transistor device disposed above the first side of the substrate;

a gate contact connecting to a portion of the gate from the second side of the substrate, the portion of the gate being adjacent to at least one of the one or more source/drain regions; and

one or more dielectric pillars disposed in the substrate, at least one of the one or more dielectric pillars being disposed in the substrate below one of the one or more source/drain regions, wherein the at least one dielectric pillar separates the gate contact from said one of the one or more source/drain regions.

18. The semiconductor structure of claim 17 , wherein each of the one or more dielectric pillars is disposed in the substrate below a corresponding one of the one or more source/drain regions.

19. A method comprising:

forming a buried power rail at least partially in a substrate, the substrate having a first side and a second side opposite the first side;

forming a gate for at least one transistor device over the first side of the substrate; and

forming a gate tie-down contact connecting the gate to the buried power rail from the second side of the substrate.

20. The method of claim 19 , further comprising:

forming one or more source/drain regions for the at least one transistor device over the first side of the substrate;

forming one or more dielectric pillars in the substrate below the one or more source/drain regions;

wherein the one or more dielectric pillars separate the gate tie-down contact from the one or more source/drain regions.