Semiconductor device and manufacturing method thereof
A semiconductor device includes a substrate, a semiconductor layer, a gate structure, source/drain regions, a bottom isolation layer, and a bottom spacer. The semiconductor layer is above the substrate. The gate structure is above the substrate and surrounds the semiconductor layer. The source/drain regions are on opposite sides of the semiconductor layer. The bottom isolation layer is between the substrate and the semiconductor layer. The bottom spacer is on a sidewall of the bottom isolation layer.
1. A semiconductor device, comprising:
a substrate;
a semiconductor layer above the substrate;
a gate structure above the substrate and surrounding the semiconductor layer;
source/drain regions on opposite sides of the semiconductor layer;
a bottom isolation layer between the substrate and the semiconductor layer;
a bottom spacer on a sidewall of the bottom isolation layer; and
an inner sidewall spacer between the gate structure and one of the source/drain regions, wherein a thickness of the inner sidewall spacer is greater than a thickness of the bottom spacer.
2. The semiconductor device of claim 1 , wherein the inner sidewall spacer is directly above the bottom spacer.
3. The semiconductor device of claim 1 , wherein the inner sidewall spacer and the bottom spacer comprise a same material.
4. The semiconductor device of claim 1 , further comprising a protection layer between the semiconductor layer and the bottom isolation layer.
5. The semiconductor device of claim 4 , wherein the bottom spacer and the bottom isolation layer are in direct contact with the protection layer.
6. The semiconductor device of claim 1 , wherein each of the source/drain regions comprises:
a bottom epitaxial structure; and
a top epitaxial structure above the bottom epitaxial structure, wherein a dopant concentration of the top epitaxial structure is greater than a dopant concentration of the bottom epitaxial structure.
7. The semiconductor device of claim 6 , wherein the bottom spacer is in direct contact with the bottom epitaxial structure and spaced apart from the top epitaxial structure.
8. The semiconductor device of claim 1 , wherein the bottom spacer is spaced apart from the gate structure.
9. A semiconductor device, comprising:
a substrate;
a bottom isolation layer above the substrate;
a channel layer above the bottom isolation layer, wherein a width of the channel layer is greater than a width of the bottom isolation layer;
a gate structure wrapping around the channel layer;
a semiconductive protection layer between the channel layer and the bottom isolation layer, wherein the semiconductive protection layer is in contact with the bottom isolation layer; and
source/drain regions connected to the channel layer.
10. The semiconductor device of claim 9 , wherein the bottom isolation layer is spaced apart from the source/drain regions.
11. The semiconductor device of claim 9 , wherein the gate structure passes through the semiconductive protection layer and is in direct contact with the bottom isolation layer.
12. The semiconductor device of claim 9 , wherein the bottom isolation layer has a seam therein.
13. The semiconductor device of claim 9 , wherein the semiconductive protection layer is spaced apart from the channel layer.
14. The semiconductor device of claim 9 , wherein the gate structure comprises:
a gate electrode wrapping around the channel layer; and
a gate dielectric layer between the gate electrode and the semiconductive protection layer.
15. A method for manufacturing a semiconductor device, comprising:
forming a semiconductor strip above a substrate, wherein the semiconductor strip comprises a plurality of first and second semiconductor layers alternately arranged;
forming a bottom dielectric isolation layer between the semiconductor strip and the substrate;
recessing the bottom dielectric isolation layer to form a first recess therein;
forming a bottom spacer in the first recess and in contact with the substrate;
removing the first semiconductor layers; and
forming a gate structure above the substrate to surround the second semiconductor layers.
16. The method of claim 15 , further comprising:
recessing the first semiconductor layers to form second recesses therein; and
forming inner sidewall spacers in the second recesses.
17. The method of claim 16 , wherein forming the inner sidewall spacers and forming the bottom spacer are performed together.
18. The method of claim 15 , further comprising forming a semiconductive cladding layer to cover the semiconductor strip prior to forming the bottom spacer.
19. The method of claim 15 , wherein the bottom spacer is spaced apart from any of the first and second semiconductor layers of the semiconductor strip.
20. The method of claim 15 , wherein a top surface of the bottom spacer is substantially coplanar with a top surface of the bottom dielectric isolation layer.