This study analyses the influence of the argon flow on the Plasma Enhanced Chemical Vapor Deposition (PECVD) of silicon oxide thin films by using TEOS as silicon source. The argon flow increases the deposition rate, however it also can creates some defects in the deposited film. Several characterization techniques were used to analyze the deposited films. The presence of argon, in the gas phase, modifies the plasma composition, the surface roughness of silicon wafer, and the surface reaction. The optimum argon flow ranges between 65 and 80 sccm to obtain a silicon oxide thin film with high quality in terms of refractive index, smoothness, and uniformity.