Molecular beam mass spectrometry has been used to observe the activation of silane, predominantly in the gas phase, during the chemical vapor deposition of Ti−Si−N thin films using Ti(NMe2)4, tetrakis(dimethylamido)titanium, silane, and ammonia at 450 °C. The extent of silane reactivity was dependent upon the relative amounts of Ti(NMe2)4 and NH3. Ti−Si−N thin films were deposited using similar process conditions as the molecular beam experiments. RBS and XPS were used to determine the atomic composition of these films. The variations of the Ti:Si ratio as a function of Ti(NMe2)4 and NH3 flows were consistent with the changes in silane reactivity under similar conditions.