We have deposited the W-N diffusion barrier on Si substrate with $NH_3$ pulse plasma enhanced atomic layer deposition (PPALD) method by using $WF_6$ and $NH_3$ gases. The $WF_6$ gas reacts with Si that the surface corrosion occurs severely, but the $NH_3$ gas incorporated with pulse plasma and $WF_6$ gas are easily deposited W-N thin film without Si surface corrosion. Because the $NH_3$ with pulse plasma can be active species dissociated and chemisorbed on Si. Thus the Si surface are covered and saturated with nitrogen, which are able to deposit the W-N thin film. We also examine the deposition mechanism and the effect of $NH_3$ pulse plasma treatment.