TaCN films were deposited at low temperature (≤400 °C) by metallorganic chemical vapor deposition (MOCVD) using pentakis(diethylamido)tantalum (PDEAT) as a precursor. The activation energy of the surface reaction is about 0.79 eV and the maximum deposition rate is about 100 Å/min at 350 °C. The resistivity of the as-deposited film decreases as the deposition temperature increases and the minimum value of resistivity obtained is 6000 μΩ-cm for the sample deposited at 400 °C. Major chemical elements in the films were detected as Ta, C, and N with some amounts of O by Auger electron spectroscopy (AES). By x-ray photoelectron spectroscopy (XPS), it is identified that the most of carbon in the films was bonded to Ta. The microstructural investigation using high resolution transmission electron microscopy reveals a nanocrystalline phase with an average grain size of about 30 Å. Preliminary investigation of the diffusion barrier property for copper showed that the 300 Å of TaCN diffusion barrier was failed after annealing at 500°C for 1 hr.