A method of producing silicon containing thin films by the thermal polymerization of a reactive gas mixture bisaminosilacyclobutane and source gas selected from a nitrogen providing gas, an oxygen providing gas and mixtures thereof. The films deposited may be silicon nitride, silicon carbonitride, silicon dioxide or carbon doped silicon dioxide. These films are useful as dielectrics, passivation coatings, barrier coatings, spacers, liners and/or stressors in semiconductor devices.