A preferred low-resistivity alpha-phase tantalum (Ta) film is directly obtained on a carbon doped oxide (SiOCH) substrate, which is treated by 5% H-2/He mixed gas plasma for 300 s, while a beta-phase Ta film is formed on fluorine silicate glass, silicon oxynitride and plasma-enhanced chemical vapor oxide substrates irrespective of the plasma treatment. The phase transformation and the resistivity change of the Ta films on the SiOCH films with respect to the plasma treatment time are investigated by X-ray diffraction analysis. Moreover, the results of X-ray photoelectron spectroscopy indicate that the formation of alpha-Ta is dependent on the surface composition of the SiOCH substrates. (c) 2005 Elsevier B.V. All rights reserved.