SrTiO3 thin films were deposited on Si(p-type 100), Pt(1000 A)/si02/Si and stepped Pt(800 Angstrom)/SiO2/Si substrates using electron cyclotron resonance plasma enhanced metal organic chemical vapor deposition (ECR-PEMOCVD) to study the effects of deposition temperature and composition on the properties of SrTiO3 thin films. The crystallinity and dielectric properties of SrTiO3 thin films were improved as the deposition temperature increased. We observed a distinct correlation, not between step coverage and deposition temperature, but between the step coverage and the composition, The composition of the film was changed by changing the flow rate of one of the carrier gas but fixing that of the other, with the deposition temperature fixed at 550 degreesC. The step coverage was improved as the composition (Sr/Ti ratio) increased up to the stoichiometric composition and C showed a saturated value of about 55% as the Sr/Ti ratio increased beyond the stoichiometric composition. This correlation was speculated based on the sticking coefficients of the precursor vapors.