A WF6-H-2-N-2 precursor system was used for plasma-enhanced chemical vapor deposition (PECVD) of WNx films. We examined the microstructural changes of the WNx films depending on N-2/H-2 flow-rate ratio and post-annealing (600-800 degrees C for 1 h). As the N-2/H-2 flow rate was increased from 0 to 1.5, as-deposited WNx films exhibited various different crystalline states, such as nanocrystalline and/or amorphous structure comprising W, WN, and W2N phases, a fine W2N granular structure embedded in an amorphous matrix, and a crystalline structure of beta-W2N phase. After post-annealing above 600 degrees C, crystalline recovery with phase separation to beta-W2N and alpha-W was observed from the WNx films deposited at an optimized deposition condition (flow-rate ratio = 0.25). From this PECVD method, an excellent step coverage of similar to 90% was obtained from the WNx films at a contact diameter of 0.4 mu m and an aspect ratio of 3.5. (c) 2006 Elsevier B.V. All rights reserved.