ZnO films deposited onto InP substrates by using sputtering has been studied. Several sputtering parameters including RF power, substrate temperature and oxygen content have been investigated to get a better ZnO thin films. The suitable ratio of oxygen and argon makes an important role in getting high guality films. 20% oxygen content is the best one for sputtered ZnO films. From SEM measurements and the etching patterns, a fine dense grain structure with a smooth interface and fine growth pattern can be obtained.