MOSFETs comprising source/drain recesses with slanted sidewall surfaces, and methods for fabricating the same
View Patent ↗The present invention relates to improved metal-oxide-semiconductor field effect transistor (MOSFET) devices with stress-inducing structures located at the source and drain (S/D) regions. Specifically, each MOSFET comprises source and drain regions located in a semiconductor substrate. Such source and drain regions comprise recesses with one or more sidewall surfaces that are slanted in relation to an upper surface of the semiconductor substrate. A stress-inducing dielectric layer is located over the slanted sidewall surfaces of the recesses at the source and drain regions. Such MOSFETs can be readily formed by crystallographic etching of the semiconductor substrate to form the recesses with the slanted sidewall surfaces, followed by deposition of a stress-inducing dielectric layer thereover.
1. A semiconductor device comprising:
a metal-oxide-semiconductor field effect transistor (MOSFET) including source and drain regions located in a semiconductor substrate, the source and drain regions separated by a channel of the MOSFET, a gate structure including at least one spacer abutting the gate structure, said source and drain regions comprise recesses with one or more sidewall surfaces that are slanted in relation to an upper surface of said semiconductor substrate, the entire recesses being separated from a portion of the semiconductor substrate underlying the gate structure by another portion of the semiconductor substrate underlying the at least one spacer, and wherein a stress-inducing dielectric layer located over said one or more slanted sidewall surfaces of said recesses at said source and drain regions, wherein a portion of stress-inducing dielectric layer is located within said semiconductor substrate beneath a level of said upper surface of said semiconductor substrate and applies stress to the channel of said MOSFET.
2. The semiconductor device of claim 1 , wherein the stress-inducing dielectric layer comprises tensilely or compressively stressed silicon nitride.
3. The semiconductor device of claim 1 , wherein the upper surface of the semiconductor substrate is oriented along one of a first set of equivalent crystal planes, and wherein the one or more sidewall surfaces of the recesses are oriented along a second, different set of equivalent crystal planes.
4. The semiconductor device of claim 3 , wherein the semiconductor substrate comprises single crystal silicon, and wherein the first and second sets of equivalent crystal planes are selected from the group consisting of the {100}, {110}, and {111} planes of silicon.
5. The semiconductor device of claim 4 , wherein the MOSFET is a p-channel MOSFET, wherein the upper surface of the semiconductor substrate is oriented along one of the {110} planes of silicon, and wherein the one or more sidewall surfaces of the recesses are oriented along the {111} planes of silicon.
6. The semiconductor device of claim 4 , wherein the MOSFET is an n-channel MOSFET, wherein the upper surface of the semiconductor substrate is oriented along one of the {100} planes of silicon, and wherein the one or more sidewall surfaces of the recesses are oriented along the {111} planes of silicon.
7. The semiconductor device of claim 1 , wherein each of the recesses has a trapezoidal cross-section with a bottom surface that is parallel to the upper surface of the semiconductor substrate.
8. The semiconductor device of claim 1 , wherein each of the recesses has a triangular cross-section without any boffom surface.
9. The semiconductor device of claim 1 , wherein said source and drain regions of said MOSFET further comprise metal silicide layers located over said slanted sidewall surfaces of said recesses and underneath said stress-inducing dielectric layer.
10. The semiconductor device of claim 1 , wherein the semiconductor substrate has a semiconductor-on-insulator (SOI) configuration and comprises a base semiconductor substrate layer, a buried insulator layer, and a semiconductor device layer, and wherein the recesses are located in the semiconductor device layer.
11. The semiconductor device of claim 1 , wherein the semiconductor substrate comprises a bulk semiconductor structure.