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 degrees C. Also. the gas-phase reaction vanished when the SiH4/WF6 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 mu Omega-cm which was comparable to that of a sputtered TiN film (about 150 mu Omega-cm) and also exhibited good adhesion ability on oxide when the temperature was higher than 200 degrees 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.