Tantalum oxide(Ta2O5)is an important material for future dynamic random access memory application owing to its high dielectric constant. This work examines the structural and electrical properties ofTa2O5thin films deposited by plasma-enhanced chemical vapor deposition using a penta ethoxy tantalumTa(OC2H5)5liquid source. The x-ray diffraction patterns indicate that the as-deposited thin films are amorphous and become polycrystalline after rapid thermal annealing above 650 °C. The level of carbon contamination is below that which can be detected by Auger electron spectroscopy measurement. Electrical measurements performed on amorphousTa2O5using aAu/Ta2O5/Pt/Ti/Simetal-tantalum oxide-metal structure exhibit a low leakage current, reasonable breakdown field (5.4 MV/cm), and high dielectric constant (23–25). The leakage current is2×10−8A/cm2at 1 MV/cm. In addition, the leakage current mechanism of amorphousTa2O5capacitors is investigated by plotting theln(J)vsE1/2curves at a low electric field (<2 MV/cm) and plottingln(J/E)vsE1/2curves at a high electric field (>2 MV/cm). The dominant conduction mechanism is due to Schottky emission at low electrical field and Poole–Frenkel emission at high electrical field. According to our results, theTa2O5thin films annealed inN2orO2at 800 °C exhibit a much higher leakage current than amorphousTa2O5 ,possibly due to the out-diffusion of Ti during high temperature annealing. ©1997 American Institute of Physics.