The present invention provides improved methods of depositing tungsten-containing films on substrates, particularly on silicon substrates. The methods involve depositing an interfacial or “flash” layer of tungsten on the silicon prior to deposition of tungsten nitride. The tungsten flash layer is typically deposited by a CVD reaction of a tungsten precursor and a reducing agent. According to various embodiments, the tungsten flash layer may be deposited with a high reducing agent to tungsten-precursor ratio and/or at low temperature to reduce attack by the tungsten precursor. In many cases, the substrate is a semiconductor wafer or a partially fabricated semiconductor wafer. Applications include depositing tungsten nitride as (or as part of) a diffusion barrier and/or adhesion layer for tungsten contacts.