The NiSi is very promising candidate for the metallization in 45 nm CMOS process such as FUSI(fully silicided) gate and source/drain contact because it exhibits non-size dependent resistance, low silicon consumption and mid-gap workfunction. Ni film was first deposited by using ALD (atomic layer deposition) technique with Bis-Ni precursor and $H_2$ reactant gas at $220^{circ}C$ with deposition rate of $1.25;{AA}/cycle$. The as-deposited Ni film exhibited a sheet resistance of $5;{Omega}/{square}$. RTP (repaid thermal process) was then performed by varying temperature from $400^{circ}C$ to $900^{circ}C$ in $N_2$ ambient for the formation of NiSi. The process temperature window for the formation of low-resistance NiSi was estimated from $600^{circ}C$ to $800^{circ}C$ and from $700^{circ}C$ to $800^{circ}C$ with and without Ti capping layer. The respective sheet resistance of the films was changed to $2.5;{Omega}/{square}$ and $3;{Omega}/{square}$ after silicidation. This is because Ti capping layer increases reaction between Ni and Si and suppresses the oxidation and impurity incorporation into Ni film during silicidation process. The NiSi films were treated by additional thermal stress in a resistively heated furnace for test of thermal stability, showing that the film heat-treated at $800^{circ}C$ was more stable than that at $700^{circ}C$ due to better crystallinity.