Gate technology for strained surface channel and strained buried channel MOSFET devices
A method of fabricating a semiconductor device including providing a semiconductor heterostructure, the heterostructure having a relaxed Si 1-x Ge x layer on a substrate, a strained channel layer on the relaxed Si 1-x Ge x layer, and a Si 1-y Ge y layer; removing the Si 1-y Ge y layer; and providing a dielectric layer. The dielectric layer includes a gate dielectric of a MISFET. In alternative embodiments, the heterostructure includes a SiGe spacer layer and a Si layer.
1. A method of fabricating a semiconductor device, the method comprising the steps of:
(a) providing a semiconductor heterostructure, the heterostructure comprising a substrate and a strained layer disposed thereover;
(b) providing at least one sacrificial layer disposed over the strained layer;
(c) removing at least a portion of the at least one sacrificial layer, thereby exposing a portion of the strained layer, wherein the strained layer remains intact after removal; and
(d) providing a gate dielectric over the exposed portion of the strained layer.
2. The method of claim 1 wherein the strained layer comprises a semiconductor material selected from the group consisting of Si, Ge, and SiGe.
3. The method of claim 1 wherein the strained layer has thickness of less than about 300 angstroms.
4. The method of claim 1 wherein the strained layer is substantially free of misfit dislocations.
5. The method of claim 1 wherein the at least one sacrificial layer comprises Si or SiGe.
6. The method of claim 1 wherein step (b) comprises providing a plurality of sacrificial layers disposed over the strained layer, the plurality of sacrificial layers including at least one sacrificial layer comprising Si and at least one sacrificial layer comprising SiGe.
7. The method of claim 1 wherein the substrate comprises Si.
8. The method of claim 7 wherein the semiconductor heterostructure comprises a relaxed Si 1-x Ge x layer disposed between the substrate and the strained layer.
9. The method of claim 8 wherein the semiconductor heterostructure comprises a buffer layer disposed between the substrate and relaxed Si 1-x Ge x layer.
10. The method of claim 7 wherein the semiconductor heterostructure comprises an insulator layer disposed over the substrate, the strained layer being disposed over the insulator layer.
11. The method of claim 1 wherein at least a portion of the at least one sacrificial layer is removed using a technique selected from the group consisting of:
wet oxidation, dry oxidation, wet etching, and dry etching.
12. The method of claim 11 wherein at least a portion of the at least one sacrificial layer is removed using the wet oxidation technique at a temperature up to about 750° C.
13. The method of claim 1 wherein step (d) comprises oxidizing at least a portion of the strained layer thereby providing the gate dielectric thereon.
14. The method of claim 1 wherein step (d) comprises depositing a dielectric layer over at least portion of the strained layer thereby providing the gate dielectric.
15. The method of claim 1 wherein step (c) comprises removing the at least one sacrificial layer.
16. The method of claim 1 , further comprising processing the semiconductor heterostructure to form a MOS device at least partially over the exposed portion of the strained layer.