High-quality Ta2O5 thin films for high-density memory devices were prepared at low temperatures by electron cyclotron resonance plasma-enhanced chemical vapor depostion (ECR-PECVD) without postannealing treatment. The effects of deposition temperature on the microstructure, composition, and electrical properties of the dielectric films were studied. The increase in deposition temperature from 145 °C to 205 °C improved the stoichiometry of the Ta2O5 thin films. As a consequence, EBD increased from 3.3 MV/cm to 4.4 MV/cm, and ∊Ta2O5, increased from 14 to 25. Interfacial SiO2 layer was observed by cross-sectional TEM, and its effects on the electrical properties of the overall dielectric film were also studied. The incubation period in which interfacial SiO2 grows was discussed with regard to reactivity between oxygen and Si substrate.