A novel silicon groove reflective grating structure (RGS) to reduce effectively the insertion loss of a high C-axis (002) thin-film zinc oxide (ZnO) surface acoustic wave (SAW) device is proposed. The insertion loss ( parameter) of three types of SAW devices was investigated and compared; one type had no RGS design, and the other two types had either a conventional metal electrode RGS or a novel etched silicon groove RGS. The wave propagation modes, the harmonic response, and the displacement amplitude profile of the proposed SAW devices were simulated by finite element analysis software (ANSYS). The implemented basic SAW device consists of a sputter-deposited high-quality ZnO thin film on the surface of a substrate. The insertion loss of the proposed SAW device with silicon groove RGS can be reduced to , which is much smaller than the insertion losses of the SAW devices with a metal electrode-type RGS () and without an RGS (). The resonant frequencies of the SAW devices studied (47.37 to 48.05 MHz) are in close agreement with the simulated results (46.8 to 47.55 MHz).