Nanocrystalline titanium nitride (TiN) thin films were deposited on Si (100) substrates using reactive DC magnetron sputtering. Microstructure of the film was modified by adjusting the N 2 flow rate during the deposition. At low flow rate, hexagonal-closed-packed (HCP)-Ti and α-Ti 2 N phases were formed. At higher N 2 flow rate, the FCC-TiN single phase was formed predominantly. FCC-TiN film showed high hardness and elastic modulus due to covalently bonded TiN cubic phase and grain size refinement. In humid atmosphere, ultra-low friction coefficient ~0.025 with high wear resistance was measured in the film consisting of HCP-Ti and α-Ti 2 N phases while the hardness was 12.7GPa.