[en] Tungsten (W) films have been selectively deposited (i.e., deposited on Si and TaSi/sub 2/ to the exclusion of SiO/sub 2/) by low pressure chemical vapor deposition vie the reduction of WF/sub 6/ by either Si of H/sub 2/. Films formed by H/sub 2/ reduction can be unlimited in thickness. However, those formed by Si reduction are self-limited in the thickness to about 150A due to the inability of WF/sub 6/ to further react with the underlying Si once such a W film is formed. Selective W films greater than about 400A thick are found to be excellent diffusion barriers between Al and Si up to an annealing temperature of 450⁰C. Their selective nature makes additional patterning and etching steps unnecessary. A mechanism of selectivity, based on the effect of glass chemistry and microstructure on their WF/sub 6/ etching rates, has been proposed. The effect of deposition parameters such as temperature and WF/sub 6/ and H/sub 2/ flow rates on the properties of the W films have been investigated. It has been found that in order to prevent excessive erosion of Si in window areas, the volumetric flow ratio of H/sub 2/ to WF/sub 6/ must be larger than critical value. Such erosion, termed ''Haloing'', is aggravated by a high state of stress at device feature interfaces. Poor adhesion of W to Si has been observed for some deposition conditions, and has been explained in terms of the incorporation of WF/sub x/ (W subfluorides) in the films. By altering process conditions, proper adhesion can readily be attained