A low dielectric constant film having silicon-carbon bonds and dielectric constant of about 3.0 or less, preferably about 2.5 or less, is provided. The low dielectric constant film is deposited by reacting a cyclic organosilicon compound and an aliphatic organosilicon compound with an oxidizing gas while applying RF power. The carbon content of the deposited film is between about 10 and about 30 atomic percent excluding hydrogen atoms, and is preferably between about 10 and about 20 atomic percent excluding hydrogen atoms.