The structural and electrical properties of RuO2 thin films deposited on Si wafers using a reactive rf magnetron sputtering system were investigated. The substrate temperature, working pressures, and sputtering gas ratios of O-2 to (Ar + O-2) were controlled from 25 to 500 degrees C, 0.66 to 13.3 Pa, and 10 to 100%, respectively. As the substrate temperature increased, the preferred orientation of the RuO2 changed from (101) to (200). Up to 400 degrees C, the grain size and structural density of the films increased, and the resistivity decreased. But the films deposited at 500 degrees C had a very rough surface morphology, considerable porosity, and a somewhat higher resistivity than that of films deposited at 400 degrees C. When the O-2 partial pressure increased, the preferred orientation of the RuO2 changed from (200) to (101), the surface roughness and the density of the films increased, and the resistivity increased. The lowest resistivity of RuO2 films obtained in this study was 1.41 x 10(-5) Omega cm at the substrate temperature of 400 degrees C and the O-2 content of 10%.