Method for forming TiON film

A TiON film forming method comprising:

• accommodating a target substrate in a processing chamber;
• maintaining an inside of the processing chamber in a depressurized state;
• and
• repeating multiple times a cycle of forming a unit TiN film at a predetermined processing temperature by alternately supplying a Ti-containing gas and a nitriding gas into the processing chamber and oxidizing the unit TiN film by supplying an oxidizing agent into the processing chamber,
• wherein in an initial stage of the film formation, a cycle of supplying the oxidizing agent after repeating the alternate supply of the Ti-containing gas and the nitriding gas X1 times is repeated Y1 times,
• wherein in a later stage of the film formation;
• a cycle of supplying the oxidizing agent after repeating the alternate supply of the Ti-containing gas and the nitriding gas X2 times is repeated Y2 times until a desired film thickness is obtained,
• wherein the number of repetition X1 in the initial stage of the film formation is set to be greater than the number of repetition X2 in the later stage of the film formation, and
• wherein the Y1 is within a range of wherein a relation between X1 and X2 is selected based on a desired film surface smoothness.