A method of forming a film having a low dielectric constant, comprises the steps of: placing a substrate between an upper electrode and a lower electrode inside a reaction chamber, introducing a silicon-containing hydrocarbon compound source gas, an additive gas, and an inert gas into a space between the upper and lower electrodes by controlling a gas flow ratio, generating a plasma by applying RF power to the space between the upper and lower electrodes in a state in which an interval between the upper electrode and the substrate is narrower in the vicinity of a center of the substrate than that in the vicinity of its periphery, and forming a film having a low dielectric constant on the substrate at a deposition rate of less than approx. 790 nm/min by controlling a flow rate of the process gas.
