Reducing transistor junction capacitance by recessing drain and source regions
View Patent ↗By recessing portions of the drain and source areas on the basis of a spacer structure, the subsequent implantation process for forming the deep drain and source regions may result in a moderately high dopant concentration extending down to the buried insulating layer of an SOI transistor. Furthermore, the spacer structure maintains a significant amount of a strained semiconductor alloy with its original thickness, thereby providing an efficient strain-inducing mechanism. By using sophisticated anneal techniques, undue lateral diffusion may be avoided, thereby allowing a reduction of the lateral width of the respective spacers and thus a reduction of the length of the transistor devices. Hence, enhanced charge carrier mobility in combination with reduced junction capacitance may be accomplished on the basis of reduced lateral dimensions.
1. A semiconductor device, comprising:
a first transistor having recessed drain and source regions, said drain and source regions are provided in recessed portions of a semiconductor layer and extend to a buried insulating layer;
a strained semiconductor alloy provided partially in said drain and source regions, said strained semiconductor alloy inducing a strain in a channel region of said first transistor, wherein a top surface of said strained semiconductor alloy opposite the buried insulating layer is recessed below an interface between a gate insulation layer and the channel region of the first transistor; and
an interlayer dielectric material formed above the top surface of said strained semiconductor alloy.
2. The semiconductor device of claim 1 , wherein said strained semiconductor alloy has a compressive strain.
3. The semiconductor device of claim 1 , wherein said strained semiconductor alloy has a tensile strain.
4. The semiconductor device of claim 1 , further comprising a second transistor of a different conductivity type relative to said first transistor, said second transistor having substantially non-recessed drain and source regions.
5. The semiconductor device of claim 1 , further comprising a second transistor of a different conductivity type relative to said first transistor, said second transistor having recessed drain and source regions extending to said buried insulating layer.
6. The semiconductor device of claim 5 , wherein said second transistor comprises a further strained semiconductor alloy differing from said strained semiconductor alloy of said first transistor.
7. The semiconductor device of claim 1 , further comprising a gate electrode structure with an electrode portion.
8. The semiconductor device of claim 7 , wherein said electrode portion represents a conductive portion of the electrode structure and has a length of approximately 50 nm and less.
9. The semiconductor device of claim 1 , having incorporated a further species into the semiconductor layer, wherein the further species is positioned such that it does not extend to the buried insulating layer.
10. The semiconductor device of claim 1 , further comprising a spacer structure that is provided with a width for substantially defining a lateral dopant profile of deep drain and source regions.
11. The semiconductor device of claim 10 , comprising further recesses whose offsets with respect to the channel region are substantially determined by the width of the spacer structure.
12. The semiconductor device of claim 10 , wherein within the drain and source regions below the spacer structure, the strained semiconductor alloy is maintained with its original thickness, thereby providing an efficient strain-inducing mechanism in the channel region.
13. The semiconductor device of claim 1 , wherein the drain and source regions further comprise an extension region.
14. The semiconductor device of claim 1 , wherein a an appropriate species is incorporated near an exposed surface of said drain and source regions to enhance the further processing of the device.
15. The semiconductor device of claim 1 , comprising a metal silicide layer formed at the top surface of said strained semiconductor alloy, and wherein the interlayer dielectric material is formed over the metal silicide layer in the recessed portion of semiconductor layer.
16. The semiconductor device of claim 1 , wherein the interlayer dielectric material is provided with an intrinsic stress to increase the strain in the channel region over the strain provided in the channel region by said strained semiconductor alloy.
17. A semiconductor device, comprising:
a first and a second transistor having drain and source regions, said drain and source regions are provided in recessed portions of a semiconductor layer and extending to a buried insulating layer,
wherein said first transistor has incorporated therein a strained semiconductor alloy and said second transistor has incorporated therein the strained semiconductor alloy for inducing a respective strain,
wherein said strained semiconductor alloy comprises recessed portions in said drain and source regions with respect to a portion provided below a gate electrode;
wherein a top surface of said strained semiconductor alloy opposite the buried insulating layer is recessed below an interface between a gate insulation layer and a channel region of the first transistor, and
wherein an interlayer dielectric material is formed above the top surface of said strained semiconductor alloy.
18. The semiconductor device of claim 17 , wherein said first transistor is a P-channel transistor and said second transistor is an N-channel transistor.
19. The semiconductor device of claim 18 , wherein the strained semiconductor alloy provides respective compressive strain in the channel region of the P-channel transistor.
20. The semiconductor device of claim 18 , wherein the strained semiconductor alloy provides respective tensile strain in the channel region of the N-channel transistor.
21. The semiconductor device of claim 17 , further comprising a spacer structure which substantially determines widths of respective recesses of said drain and source regions.
22. The semiconductor device of claim 17 , wherein said drain and source regions comprise an extension region and a deep drain and source region.
23. The semiconductor device of claim 17 , wherein a metal silicide layer is formed at the top surface of said strained semiconductor alloy, and wherein the interlayer dielectric material is formed over the metal silicide layer in the recessed portion of semiconductor layer.
24. The semiconductor device of claim 17 , wherein the interlayer dielectric material is provided with an intrinsic stress to increase the strain in the channel region over the strain induced by said strained semiconductor alloy.