A fully silicided (FUSI) metal gate process is merged with ultimate spacer process (USP) strain engineering to effectively enhance the performances of deep nano complementary metal oxide semiconductor field effect transistor (CMOSFET). Using the merged FUSI-USP process, the FUSI gate can be processed with the source/drain region silicide in one step, and the poly gate can be thinned to less than 300 angstrom, thus shortening the distance between the strain contact etch stop layer and the channel to generate higher stress. Therefore, Ion gain up to 28% can be achieved in an n type MOSFET with tensile-stress, and 40% in a p type MOSFET with compressive-stress. (c) 2008 Elsevier B.V. All rights reserved.