Transistor having a channel with tensile strain and oriented along a crystallographic orientation with increased charge carrier mobility
View Patent ↗By appropriately orienting the channel length direction with respect to the crystallographic characteristics of the silicon layer, the stress-inducing effects of strained silicon/carbon material may be significantly enhanced compared to conventional techniques. In one illustrative embodiment, the channel may be oriented along the <100> direction for a (100) surface orientation, thereby providing an electron mobility increase of approximately a factor of four.
1. A semiconductor device, comprising:
a first transistor having a first channel region defining a first channel length direction, said first channel region comprising a crystalline silicon material with a tensile strain component oriented along said first channel length direction, said first channel length direction being oriented substantially along a crystallographic <100> direction for a semiconductor layer having a (100) surface orientation.
2. The semiconductor device of claim 1 , wherein said silicon material in said first channel region further exhibits a compressive strain acting along a first channel width direction.
3. The semiconductor device of claim 1 , further comprising drain and source regions formed adjacent to said first channel region, said drain and source regions comprising a strained semiconductor material.
4. The semiconductor device of claim 3 , wherein said strained semiconductor material comprises a silicon/carbon material.
5. The semiconductor device of claim 4 , wherein a carbon concentration in said strained silicon/carbon material is approximately 1.5 atomic percent or higher.
6. The semiconductor device of claim 1 , further comprising a second transistor having a second channel region defining a second channel length direction having a different orientation relative to said first channel length direction.
7. The semiconductor device of claim 6 , wherein said second channel region comprises a strained silicon material having a compressive strain along said second channel length direction.
8. The semiconductor device of claim 1 , further comprising a first stressed dielectric layer formed above said first transistor, said first dielectric layer having a tensile stress.
9. The semiconductor device of claim 1 , further comprising a second transistor having a second channel region, a length of said second channel region being oriented along said first channel length direction, said second channel region comprising silicon having a crystallographic orientation along said first channel length direction that differs from the <100> direction.
10. The semiconductor device of claim 3 , wherein the strained semiconductor material is positioned with a moderately high offset to said first channel region.
11. The semiconductor device of claim 3 , wherein the strained semiconductor material is positioned very close to the channel region.
12. The semiconductor device of claim 11 , wherein metal silicide regions are provided within the strained semiconductor material and a gate electrode.
13. The semiconductor device of claim 6 , wherein the different orientation is along a <110> direction.
14. A semiconductor device, comprising:
a substrate having formed thereon a silicon-based semiconductor layer, wherein the semiconductor layer has a (100) surface orientation; and
a notch provided in the substrate which indicates a <100> crystallographic direction such that a first channel region, defining a first channel length direction, of a first transistor element is automatically oriented along the <100> direction.
15. The semiconductor device of claim 14 , further comprising a second transistor element having a second channel region defining a second channel length direction having a different orientation relative to said first channel length direction.
16. The semiconductor device of claim 15 , wherein the different orientation is along a <110> direction.
17. The semiconductor device of claim 15 , in which the surface orientation is (110) such that corresponding crystallographic orientations <110> and <100> have an angular offset of 90 degrees.
18. The semiconductor device of claim 17 , wherein the second transistor represents an N-channel transistor.
19. The semiconductor device of claim 18 , wherein a compressive stress component is oriented along the <110> crystallographic orientation and a tensile stress component is oriented along the <100> crystallographic orientation.