(SrxTi1-x)O-3 (0.26 less than or equal to s less than or equal to 0.55) thin films were prepared on p-type Si (100) and Pt/SiO2/Si substrates. A stoichiometric perovskite SrTiO3 film with good thickness and composition uniformity was obtained on 4 inch wafer (+/-7% temperature uniformity) using electron cyclotron resonance (ECR) plasma which compensated for the substrate temperature difference. It was found that the activity of the precursors can be controlled by changing the ECR plasma power and O-2-to-(Ar + O-2) flow rate ratio. The deposition rate and the Sr-to-Ti composition ratio of the films were increased with the ECR plasma power and the O-2-to-(Ar + O-2) flow rate ratio of the ECR plasma, because the activation and decomposition of the sourer of strontium vapor are more easily affected by the ECR oxygen plasma power than those of the source of titanium vapor. The crystallinity and the orientation of the film were controlled by its Sr-to-Ti composition ratio and oxygen activity or oxygen partial pressure. The films showed a uniform and fine grain structure, and a Sr-to-Ti composition dependence.