Transistor channel having vertically stacked nanosheets coupled by fin-shaped bridge regions
Embodiments of the present invention are directed to techniques for providing an novel field effect transistor (FET) architecture that includes a center fin region and one or more vertically stacked nanosheets. In a non-limiting embodiment of the invention, a nanosheet stack is formed over a substrate. The nanosheet stack can include one or more first semiconductor layers and one or more first sacrificial layers. A trench is formed by removing a portion of the one or more first semiconductor layers and the one or more first sacrificial layers. The trench exposes a surface of a bottommost sacrificial layer of the one or more first sacrificial layers. The trench can be filled with one or more second semiconductor layers and one or more second sacrificial layers such that each of the one or more second semiconductor layers is in contact with a sidewall of one of the one or more first semiconductor layers.
1. A method for forming a semiconductor device, the method comprising:
forming a nanosheet stack over a substrate, the nanosheet stack comprising one or more first semiconductor layers and one or more first sacrificial layers;
forming a trench by removing a portion of the one or more first semiconductor layers and the one or more first sacrificial layers, the trench exposing a surface of a bottommost sacrificial layer of the one or more first sacrificial layers; and
filling the trench with one or more second semiconductor layers and one or more second sacrificial layers such that each of the one or more second semiconductor layers is in contact with a sidewall of one of the one or more first semiconductor layers.
2. The method of claim 1 , wherein the one or more first semiconductor layers comprise silicon and the one or more first sacrificial layers comprise silicon germanium.
3. The method of claim 2 further comprising forming a third sacrificial layer between the bottommost sacrificial layer.
4. The method of claim 3 , wherein the third sacrificial layer comprises silicon germanium having a higher germanium concentration than the bottommost sacrificial layer.
5. The method of claim 1 , wherein the one or more first semiconductor layers each comprise a height of about 8 nm.
6. The method of claim 1 , wherein the bottommost sacrificial layer and a topmost sacrificial layer of the one or more first sacrificial layers comprise a height of about 10 nm and the remaining sacrificial layers of the one or more first semiconductor layers each comprise a height of about 20 nm.
7. The method of claim 1 , wherein the trench comprises a width of about 5 nm.
8. The method of claim 3 further comprising forming a shallow trench isolation adjacent to the nanosheet stack.
9. The method of claim 8 further comprising recessing the shallow trench isolation below a surface of the third sacrificial layer.
10. The method of claim 3 further comprising removing the third sacrificial layer selective to the one or more first sacrificial layers and the one or more second sacrificial layers to define a cavity.
11. The method of claim 10 further comprising filling the cavity with a bottom spacer.
12. The method of claim 1 further comprising removing the one or more first sacrificial layers and the one or more second sacrificial layers.
13. The method of claim 1 further comprising forming a gate over the nanosheet stack.
14. A method for forming a semiconductor device, the method comprising:
forming a first channel region over a substrate, the first channel region comprising a first vertical fin and a first nanosheet extending from a sidewall of the first vertical fin;
forming a second channel region over the first channel region, the second channel region comprising a second vertical fin and a second nanosheet extending from a sidewall of the second vertical fin; and
forming a gate over the first channel region and the second channel region, the gate in contact with a topmost surface of the first channel region and a bottommost surface of the second channel region.
15. The method of claim 14 further comprising forming a bottom spacer between the first channel region and the substrate.