Amorphous W-B-N thin films were deposited with the plasma enhanced chemical vapor deposition method. The stoichiometry of W-B-N changed from W9B5N5 to W38B42N20 while the flow ratio of B10H14/NH3 varied from 2 to 6 under the condition that the flow ratio of WF6 and NH3 were fixed. During annealing process at 800degreesC for 30 min, the W90B5N5 and W80B15N5 films were completely changed into a (100) oriented alpha-W film. Until the B and N contents in the as-deposited W-B-N film were lower than the W51B3N19 the B and N atoms were out-diffused. Whereas the B and N contents were higher than when the W51B30N19 B-N bond was formed, which prevented the grain growth of W or W-N phases in W-B-N thin film during the annealing process. Formation of the B-N bond in W-B-N thin film is more effective to inhibit the out-diffusion of B and N.