A method of forming dielectric film having Si—N bonds on a semiconductor substrate by plasma enhanced atomic layer deposition (PEALD), includes: introducing a nitrogen- and hydrogen-containing reactive gas and a rare gas into a reaction space inside which the semiconductor substrate is placed; introducing a hydrogen-containing silicon precursor in pulses of less than 1.0-second duration into the reaction space wherein the reactive gas and the rare gas are introduced; exiting a plasma in pulses of less than 1.0-second duration immediately after the silicon precursor is shut off; and maintaining the reactive gas and the rare gas as a purge of less than 2.0-second duration.