The structural properties of r.f.-sputtered ZnO films prepared onto a Ru/Si and an Al/Si substrate were investigated. The ZnO films were deposited at a substrate temperature of 350 degrees C, O-2/Ar ratio of 3/7, working pressure of 0.8 Pa, and r.f. power of 80 W. The (002) peak intensity of the ZnO films on the Ru/Si is about five times stronger than that of the ZnO film on the Al/Si substrate. For the ZnO film deposited on the Al/Si substrate, the crystallite size was 312.75 Angstrom and the biaxial stress was -9.86 x 10(8) Pa. For the ZnO films on the Ru/Si substrate, the crystallite size was 333.66 Angstrom and biaxial stress was -1.37 x 10(8) Pa. The ZnO films on the Ru/Si substrate have a much denser structure than the ZnO films do on the Al/Si substrate. It has been found that the Ru/Si substrate is a very suitable substrate for growing the ZnO films.