Silicon nitride and oxide films have been formed using a photo-CVD apparatus with a microwave-excited VUV lamp. The lamp used was a D2 lamp or a rare gas resonance line lamp such as Xe and Kr. For the nitride film deposited at 320 °C, the BHF etching rate of the film, 40–70Å/min, is lower by less than one-tenth than that deposited using a conventional low-pressure Hg lamp, indicating formation of a high density film. The deposition rate has been enhanced dramatically from 13Å/min to 100Å/min by incorporating the photo-ionization assisted effect, which is brought about by an ionization of a substrate surface and by ions formed by collisions of reactant gases with photoelectrons and photo-ionized ions. The BHF etching rate of the oxide film is considerably lower than those formed using a Hg lamp and excimer lasers, and is similar to that using conventional PE-CVD. Conformal step coverage has been obtained for both the silicon nitride and oxide films.