The effect of the , , on film composition and structure have been investigated using He backscattering, infrared absorption, ellipsometry, and electron spin resonance. Films were deposited at 770°C with an ranging from 0.1 to 10 at reduced pressure in hot wall reactor. The composition of film with was found to be nearly stoichiometric, whereas silicon‐rich films were obtained when decreased. To be silicon‐rich, nitrogen atoms should be coordinated with less than three silicon atoms as a result of the formation of N‒H or N‒N bonds. However, in the present work, the concentration of N‒H bonds was so small that nitrogen‐rich film was not obtained. The refractive index on the was deduced to be a bonding‐density‐weighted linear combination of , and . An ESR signal with a g‐value of 2.003 was found for silicon‐rich films, and was associated with silicon dangling bonds. Annealing at 1100°C caused complete effusion of hydrogen atoms, but a slight increase in ESR spin density. This indicated that formation of Si‒N bonding or valence alternation pairs during the annealing was responsible for rather small ESR spin density.