Formation of a super steep retrograde channel
View Patent ↗Systems and methods for raised source/drain with super steep retrograde channel. In accordance with a first embodiment of the present invention, in one embodiment, a semiconductor device comprises a substrate comprising a surface and a gate oxide disposed above the surface comprising a gate oxide thickness. The semiconductor device further comprises a super steep retrograde channel region formed at a depth below the surface. The depth is about ten to thirty times the gate oxide thickness. Embodiments in accordance with one embodiment may provide a more desirable body biasing voltage to threshold voltage characteristic than is available under the conventional art.
1. A method comprising:
forming a gate oxide over a substrate surface; and
forming a super steep retrograde channel at a depth below the substrate surface, wherein the depth is at least ten times a thickness of the gate oxide.
2. The method of claim 1 , further comprising:
disposing the substrate, wherein the substrate is configured to accept a body biasing voltage.
3. The method of claim 1 , further comprising:
forming a source structure above the substrate surface.
4. The method of claim 3 , wherein the source structure comprises epitaxially-grown material.
5. The method of claim 3 , wherein the source structure comprises silicide.
6. The method of claim 3 , further comprising:
forming a source extension beneath the source structure, wherein the source extension is separate from the super steep retrograde channel.
7. The method of claim 1 , wherein a horizontal extent of the super steep retrograde channel region is substantially limited to a horizontal extent of the gate oxide.
8. A method comprising:
forming a super steep retrograde channel region within a substrate, wherein a threshold voltage of the super steep retrograde channel region changes substantially linearly with a change in body biasing voltage; and
forming a raised source structure on the substrate.
9. The method of claim 8 , further comprising:
coupling a body biasing voltage to the super steep retrograde channel region.
10. The method of claim 8 , further comprising:
forming a gate oxide above a surface of the substrate, wherein a depth of the super steep retrograde channel region is substantially within the range of ten to thirty times a thickness associated with the gate oxide.
11. The method of claim 10 , wherein a horizontal extent of the super steep retrograde channel region is substantially limited to a horizontal extent of the gate oxide.
12. The method of claim 8 , wherein a one-unit change in applied body biasing voltage produces a change in the threshold voltage substantially within the range of one tenth to one third of the one-unit change.
13. The method of claim 8 , further comprising:
forming a spacer, wherein the spacer insulates the raised source structure.
14. The method of claim 8 , wherein said forming a super steep retrograde channel region comprises using a masked implant.
15. The method of claim 8 , further comprising:
forming a shallow source extension, wherein the shallow source extension is separate from the super steep retrograde channel region; and
forming a shallow drain extension, wherein the shallow drain extension is separate from the super steep retrograde channel region.