Method for forming film by plasma-assisted deposition using two-frequency combined pulsed RF power

A method for forming a dielectric film on a substrate by plasma-assisted deposition, comprising:

• introducing a Si-containing process gas to a reaction space wherein a substrate having a surface with patterned recesses is placed;
• and
• applying RF power in pulses to the process gas in the reaction space to form a dielectric film on the surface by plasma reaction, said RF power comprised of pulses of high-frequency RF power having a frequency of about 10 MHz to about 30 MHz and pulses of low-frequency RF power having a frequency of about 200 kHz to about 1MHz, wherein the pulses of high-frequency RF power, which is pulsed in cycles, and the pulses of low-frequency RF power, which is pulsed in cycles, overlap and are synchronized, wherein a cycle duration including each pulse of high-frequency RF power and a cycle duration including each pulse of low-frequency RF power are in a range of approximately 0.1 milliseconds to approximately 10 milliseconds,
• each pulse of high-frequency RF power being composed of a plurality of cycles defined by the frequency, each pulse of low-frequency RF power being composed of a plurality of cycles defined by the frequency, wherein a duty ratio of each cycle of the plurality of cycles constituting each pulse of high-frequency RF power and a duty ratio of each cycle of the plurality of cycles constituting each pulse of low-frequency RF power are 75% or less.