Go-sputtered Ru-Ti alloy films were studied for use as a bottom electrode for ferroelectric/paraelectric thin film capacitors. The Ru/Ti ratio in the alloy was found to strongly affect the resistivity, structure formation and thermal stability. The resistivity of the as-deposited films decreases and approaches that of pure Ru metal films as the amount of Ru atoms increases. From X-ray diffraction measurements, it was found that the RuTi phase has formed for the as-deposited sample. The resistivity of alloy thin films is thermally stable as the Ru composition varies from 0.68 to 0.81. It may be due to RuTiO2 formation at the surface and play an important role in preventing further oxidation of the Ru-enriched layer. This oxide also exhibits conductive behavior. On the other hand, the interface between Ru-enriched alloys and Si substrate was still sharp for the sample treated by rapid thermal processing at 600 degrees C for 1 min. The alloy film with high Ru composition shows excellent thermal stability and barriers against interdiffusion of Si and oxygen.