A method of forming a conformal dielectric film having Si—N bonds on a substrate having a patterned surface includes: introducing a reactant gas into a reaction space; introducing a silicon precursor in pulses of less than 5-second duration into the reaction space; applying a first RF power to the reaction space during the pulse of the silicon precursor; applying a second RF power to the reaction space during the interval of the silicon precursor pulse, wherein an average intensity of the second RF power during the interval of the silicon precursor pulse is greater than that of the first RF power during the pulse of the silicon precursor; and repeating the cycle to form a conformal dielectric film having Si—N bonds with a desired thickness on the patterned surface of the substrate.