Stoichiometry dependence of Fermi-level pinning in a fully silicided (FUSI) NiSi gate on high-K dielectric is investigated. A higher composition ratio of Si in NiSi shows a higher degree of Fermi-level pinning. It has also been found that there is a critical ratio (C-crit) above which there is no Fermi-level pinning, and the C-crit depends on the underlying gate dielectric material also.