This paper gives characterization of ZnO thin film deposited by RF magnetron sputtering method, which is concerned in deposition process and device fabrication process, to fabricate solidly mounted resonator(SMR)-type film bulk acoustic resonator(FBAR). A piezoelectric layer of 1.1${mu}{ extrm}{m}$ thick ZnO thin films were grown on thermally oxidized SiO$_2$(3000 $AA$)/Si substrate layers by RF magnetron sputtering at the room temperature. The highly c-axis oriented ZnO thin film was obtained at the conditions of 265 W of RF power, 10 mtorr of working pressure, and 50/50 of Ar/O$_2$ gas ratio. The piezoelectric-active area was 50 ${mu}{ extrm}{m}$${ imes}$50${mu}{ extrm}{m}$, and the thickness of ZnO film and Al-3 % Cu electrode were 1.4 ${mu}{ extrm}{m}$ and 180${mu}{ extrm}{m}$, respectively. Its series and parallel frequencies appeared at 2.128 and 2.151 GHz, respectively, and the qualify factor of the resonator was as high as 401.8$pm$8.5.