Semiconductor device comprising a metal gate stack of reduced height and method of forming the same
By providing a CMP stop layer in a metal gate stack, the initial height thereof may be efficiently reduced after the definition of the deep drain and source areas, thereby providing enhanced process conditions for forming highly stressed dielectric materials. Consequently, the dielectric material may be positioned more closely to the channel region substantially without deteriorating gate conductivity.
1. A method, comprising:
forming a gate electrode structure of a transistor above a semiconductor layer, said gate electrode structure comprising a high-k dielectric layer, a metal-containing material formed on said high-k dielectric layer and a mask material formed above said metal-containing material;
forming drain and source regions in said semiconductor layer by using said gate electrode structure as an implantation mask;
removing at least a portion of said mask material of said gate electrode structure to reduce a height of said gate electrode structure; and
forming a strain-inducing dielectric layer above said drain and source regions and said gate electrode structure of reduced height, said strain-inducing dielectric layer generating strain in a channel region of said transistor.
2. The method of claim 1 , wherein forming said gate electrode structure comprises forming a first layer of said mask material having a first material composition and forming a second layer above said first layer, wherein said second layer has a second material composition that differs from said first material composition.
3. The method of claim 2 , wherein removing at least a portion of said mask material comprises removing said second layer by a removal process and using said first layer for controlling said removal process.
4. The method of claim 3 , wherein said removal process comprises a chemical mechanical planarization process.
5. The method of claim 1 , wherein removing said at least a portion of said mask material comprises forming a fill material so as to embed said gate electrode structure in said fill material and removing said at least a portion of said mask material together with a portion of said fill material.
6. The method of claim 5 , further comprising annealing said transistor in the presence of a remaining portion of said fill material.
7. The method of claim 6 , wherein said fill material comprises silicon nitride.
8. The method of claim 1 , further comprising forming a metal silicide at least in said drain and source regions.
9. The method of claim 8 , wherein said metal silicide is formed prior to removing said at least a portion of said mask material.
10. The method of claim 8 , wherein said mask material comprises a first layer and a second layer and wherein said metal silicide is formed after removing said second layer of the mask material while maintaining said first layer of the mask material when forming said metal silicide.
11. A method, comprising:
forming a first gate electrode structure of a first transistor above a semiconductor layer, said first gate electrode structure comprising a high-k dielectric material a first metal-containing material, and a mask material;
forming a second gate electrode structure of a second transistor, said second gate electrode structure comprising a high-k dielectric material a second metal-containing material, and said mask material;
defining drain and source regions of said first and second transistors in said semiconductor layer by implanting dopant species and using said first and second gate electrode structures as implantation masks;
reducing a height of said first and second gate electrode structures after defining said drain and source regions; and
forming a first strain-inducing layer above said first gate electrode structure of reduced height and a second strain-inducing layer above said second gate electrode structure of reduced height, the first and second strain-inducing layers generating a different type of strain.
12. The method of claim 11 , wherein forming said first and second gate electrode structures comprises forming a removal control layer above said first and second metal-containing materials and forming said mask material on said removal control layer.
13. The method of claim 12 , wherein reducing a height of said first and second gate electrode structures comprises performing a removal process to remove said mask material and using said removal control layer for controlling said removal process.
14. The method of claim 13 , wherein said removal process comprises a chemical mechanical planarization process.
15. The method of claim 13 , wherein said removal process comprises an etch process.
16. The method of claim 13 , further comprising forming a fill material at least between said first and second gate electrode structures and removing a portion of said fill material during said removal process.
17. The method of claim 12 , wherein forming said first and second strain-inducing layers comprises forming said first strain-inducing layer above said first and second gate electrode structures and removing said first strain-inducing layer from above said second gate electrode structure using said removal control layer as an etch stop.
18. The method of claim 16 , further comprising annealing the drain and source regions of said second transistor prior to forming the drain and source regions of said first transistor and annealing the drain and source regions of said first transistor in the presence of at least a portion of said fill material.