Methylamine (CH3NH2) was employed with SiH4 to deposit amorphous silicon carbon nitride films due to its easy dissociation as well as containing both carbon and nitrogen elements. The effect of dilution gas, such as H-2, N-2, Ar and He on the film growth was studied in electron cyclotron resonance plasma chemical vapor deposition (CVD) reactor. At a microwave power of 250 W and a substrate temperature of 700 degreesC, ternary silicon carbon nitride film has been successfully deposited using He as dilution gas. However, only binary silicon nitride films were formed using dilution gases of Ar, N-2 and H-2 but otherwise similar conditions. Characterization of the films using FTIR, XPS and optical emission study of the plasma were employed to study the growth process. Possible explanations and discussion for the growth behaviors of the dilution gases are presented.