Nickel silicide is promising to be the choice material as contact to the source, drain, and gate for sub-65 nm and 45 nm CMOS devices. However, the thermal stability of NiSi is worse as the high resistivity phase of NiSi2 nucleates at about 750 °C and film agglomeration occurs even at a temperature as low as 600 °C. The process integration issues and formation thermally stable NiSi are needed to be understood and addressed. In order to obtain a thermally stable Ni-FUSI gate electrode, we introduced a novel integration process by using a two-step anneal process associating with properly tuned thickness of the initial Ni film and implant BF2 atoms during the poly-gate formation. As results, push the transformation of NiSi2 to a higher temperatures at about 900 °C. Several measurement techniques such as XRD, TEM, SEM and Resistivity are carried out to demonstrate its physical and electrical properties.