Ternary films about 200 nm thick of composition Ru20Si15O65 have been synthesized by reactive rf magnetron sputtering of a Ru,Sit target in an argon-oxygen gas. As-deposited, the films are X-ray-amorphous. Their atomic density is 8.9 X 10(22)/cm(3) (5.1 g/cm(3)), and their electrical resistivity is in the range of 2 m Ohm cm. After annealing in dry oxygen at 600 degrees C for 30 min, micron-sized grains of RuO2 grow out of the film and volatile RuO4 escapes. The significant of these results is discussed.