Ruthenium and ruthenium oxide films were deposited on a Ru/SiO2/Si substrate at 355°C using a Ru(C2H5C5H4)2- [Ru(EtCp)2] precursor and oxygen gas. The effects of the oxygen flow rate on film composition, microstructure, surface morphology, stress, and resistivity were investigated. The oxygen content in the film increases as the oxygen flow rate increases and saturates at a flow of 1200 sccm. Films deposited with an O2 flow rate of 800 sccm or less have the structure of the ruthenium phase, a <001> texture, and smooth surface morphology. Films deposited with an O2 flow rate of 1200 sccm or above have the structure of the ruthenium dioxide phase and higher surface roughness. Ru-phase films have a high stress level and low resistivity; the increase of oxygen flow rate from 50 to 800 sccm results in a decrease of stress from 8 to 5 G dyn/cm2 and an increase of resistivity from 19 to 48 μΩ cm. RuO2-phase films have a relatively low stress level (2 G dyn/cm2), which does not change significantly with the oxygen flow rate, and high resistivity which slightly decreases from 120 to 115 μΩ cm as the oxygen flow rate increases from 1200 to 2000 sccm.