In this work, the thin tungsten film nucleated by an in situ SiH4-WF6 gas-phase reaction in the low pressure regime (100 mTorr) was investigated and used as an adhesion layer to replace TiN in a blanket chemical vapor deposition of tungsten (CVD-W) process. The deposition rate, step coverage, and film resistivity were studied as a function of the process parameters. Deposition rates from 360 to over 3000 nm/min were observed and increased with increasing deposition pressure and temperature. Moreover, we found that the deposition rate fell to zero when the temperature was less than 150°C. Also, the gas-phase reaction vanished when the SiH4/WF4 flow ratio was smaller than 1.6. On the other hand, the step coverage decreased with increasing deposition rate. Finally, the tungsten film resistivity was 167 μΩ-cm which was comparable to that of a sputtered TiN film (about 150 μΩ-cm) and also exhibited good adhesion ability on oxide when the temperature was higher than 200°C. Overall, the results indicate that this in situ gas-phase nucleated tungsten film is an attractive replacement for TiN film in the blanket CVD-W technique because of reduced process complexity, excellent step coverage, and low resistivity.