W deposition by reduction of is a promising alternative for W deposition from and . The structure and composition of W layers deposited from and , are determined mainly by the deposition temperature. At temperatures between 300 and 400°C, W layers with the A15 bcc β‐W crystal structure are formed. These β‐W layers contain a substantial amount of homogeneously distributed Ge, roughly between 10 and 15 atomic percent (a/o). At higher temperatures, films are formed which consist of a mixture of β‐W and α‐W. At temperatures greater than 500°C, the layers consist exclusively of α‐W, and the Ge concentration is less than 1 a/o. The amount of β‐W in the film correlates with the resistivity and the amount of incorporated Ge. The incorporated Ge may promote the formation of the β‐W phase. Other process parameters, such as the total pressure and the ratio, have a minor effect on the structure and composition of the films. The β‐W deposited at ≈375°C is well suited for use as contact material to active Si areas of ULSI circuits. The contact resistivity of the β‐W layers to contacts is as low as the contact resistivity of annealed Al(Si 1%)/Si reference samples. The contact resistivity to the p+ diffusions was slightly higher than to the n+ diffusions. No leakage current was observed, indicating that no harmful attack of the active Si areas occurred during the deposition of β‐W. High resolution SEM pictures confirmed the absence of any significant Si consumption, encroachment, or tunnels at the Si interface. The β‐W layers are stable and transform to α‐W only at temperatures greater than 600°C during 30‐min anneals. After transformation to α‐W, silicidation to occurs. The β‐W is an effective diffusion barrier between Al and Si. During 30‐min anneals at 500°C, a β‐W film as thin as 60 nm prevented all Al/Si interdiffusion. A 120 nm thick β‐W film prevented Al/Si interdiffusion to at least 540°C. Finally, a deposition sequence consisting of the reduction of followed by or reduction of , combines the excellent interface properties of the process with the higher growth rate and better selectivity of the or process.