A method for forming a dielectric film is disclosed. The method includes (a) exposing a substrate to a first gas pulse having a first oxygen-containing gas in a chamber; (b) exposing the substrate to multiple consecutive second gas pulses having a second oxygen-containing gas in the chamber, wherein the first oxygen-containing gas is different from the second oxygen-containing gas; and (c) sequentially after (a) and (b), exposing the substrate to a third gas pulse having a metal-containing gas in the chamber. Steps (a), (b), and (c) may be repeated any number of times to form the dielectric film with a predetermined thickness.