In this work, the Co film was deposited by chemical vapor deposition (CVD) on TaN(x)/SiO2/Si substrate at various NH3/H2 gas flow ratio (0, 0.08, 0.11, 0.17, 0.2) to form the continuous layer. It was found that Co film can achieve a low resistivity of 63 microomega-cm, high nucleation density, and a low root-mean-square roughness of 0.79 nm at 0.17 of NH3/H2 gas flow ratio. Moreover, by using fourier transform infrared spectroscopy (FT-IR) analysis, the effect of NH3 gas was confirmed as a reaction catalyst.