Trenches in a layer of SiO2on Si, with feature sizes down to 0.125 μm have been filled with tungsten (W) using selective chemical vapor deposition (CVD). The trenches were formed in a fashion similar to contact vias by reactive ion etching the SiO2to the underlying silicon. The tungsten was then deposited in a cold wall CVD reactor, by silane reduction of WF6, to a thickness of 0.5 μm. The process results in good planarity and uniformity making it suitable for the fabrication of sub‐0.5 μm contacts and interconnects, and for the formation of high aspect ratio absorbers in x‐ray masks.