Nanosheet mosfet with isolated source/drain epitaxy and close junction proximity
A sacrificial inner dielectric spacer is formed on physically exposed sidewalls of each recessed semiconductor channel material nanosheet of a nanosheet material stack that further includes recessed sacrificial semiconductor material nanosheets that have an inner dielectric spacer formed on physically exposed sidewalls thereof. A local isolation region is then formed by selective epitaxial growth on a surface of a semiconductor substrate containing the nanosheet material stack. After forming the local isolation region, the sacrificial inner dielectric spacers are removed and a source/drain region is formed on the physically exposed surface of each recessed semiconductor channel material nanosheet. A portion of the source/drain structure is formed in a gap located between each neighboring pair of vertically spaced apart inner dielectric spacers.
1. A semiconductor structure comprising:
a plurality of stacked and suspended semiconductor channel nanosheets located above a semiconductor substrate;
a functional gate structure surrounding a portion of each semiconductor channel nanosheet of the plurality of stacked and suspended semiconductor channel nanosheets, wherein a bottommost surface of the functional gate structure that is located beneath a bottommost semiconductor channel nanosheet of the plurality of stacked and suspended semiconductor channel nanosheets directly contacts the semiconductor substrate;
an inner dielectric spacer located on a sidewall of the functional gate structure and present above and beneath each semiconductor channel nanosheet of the plurality of stacked and suspended semiconductor channel nanosheets;
a source/drain (S/D) structure located on each side of the functional gate structure, wherein a portion of the S/D structure physically contacts a sidewall of each of the semiconductor channel nanosheets and is present in a gap located between each neighboring pair of vertically spaced apart inner dielectric spacers; and
a local isolation region present between the source/drain structure and the semiconductor substrate, wherein an entirety of a topmost surface of the local isolation region directly contacts a bottommost surface of the S/D structure, and wherein at least a portion of a sidewall of the local isolation region directly contacts a sidewall of a bottommost inner dielectric spacer that is located beneath the bottommost semiconductor channel nanosheet of the plurality of stacked and suspended semiconductor channel nanosheets.
2. The semiconductor structure of claim 1 , wherein the local isolation region is composed of an epitaxial oxide that is lattice matched to an upper portion of the semiconductor substrate.
3. The semiconductor structure of claim 2 , wherein the epitaxial oxide is composed of lanthanum (II) oxide, gadolinium(III)-oxide, dysprosium(III)-oxide, holmium(III) oxide, erbium (III) oxide, thulium (III) oxide, lutetium(III) oxide, cerium (IV) oxide, lanthanum-yttrium oxide, gadolinium-erbium oxide, neodymium-erbium oxide, neodymium-gadolinium oxide, or lanthanum-erbium oxide.
4. The semiconductor structure of claim 1 , wherein the local isolation region is composed of a semi-insulating wide bandgap semiconductor material.
5. The semiconductor structure of claim 4 , wherein the semi-insulating wide bandgap semiconductor material is composed of chromium doped GaP.
6. The semiconductor structure of claim 1 , wherein the local isolation region is present on a recessed surface of the semiconductor substrate.
7. The semiconductor structure of claim 1 , wherein the plurality of stacked and suspended semiconductor channel nanosheets is located on a pedestal portion of the semiconductor substrate.
8. The semiconductor structure of claim 1 , further comprising an interlayer dielectric material layer on the source/drain structure.
9. The semiconductor structure of claim 8 , further comprising a contact structure contacting a surface of the source/drain structure and embedded in the interlayer dielectric material.