Several commercially available organometallic precursors have been evaluated for metallorganic chemical vapor deposition (MOCVD) of pure ruthenium films. Of these, only a dimer, [RuC5H5(CO)(2)](2), proved suitable for CVD. On patterned Si3N4 and flat barium strontium titanate (BST), pure, conductive, conformal ruthenium films were grown from this dimer when oxygen was used as a reaction gas. Without oxygen, significant amounts of carbon were incorporated into the film. Oxygen and substrate temperature effects on ruthenium CVD film growth were investigated by resistivity measurements, in situ X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), and scanning electron microscopy (SEM). Growth conditions and possible mechanisms are discussed.