To observe the formation of defects at the interface between an oxide semiconductor and SiO2, ZnO was prepared on SiO2 with various oxygen gas flow rates by RF magnetron sputtering deposition. The crystallinity of ZnO depends on the characteristic of the surface of the substrate. The crystallinity of ZnO on a Si wafer increased due to the activation of ionic interactions after an annealing process, whereas that of ZnO on SiO2 changed due to the various types of defects which had formed as a result of the deposition conditions and the annealing process. To observe the chemical shift to understand of defect deformations at the interface between the ZnO and SiO2, the O 1s electron spectra were convoluted into three sub-peaks by a Gaussian fitting. The O 1s electron spectra consisted of three peaks as metal oxygen (at 530.5 eV), O2. ions in an oxygendeficient region (at 531.66 eV) and OH bonding (at 532.5 eV). In view of the crystallinity from the peak (103) in the XRD pattern, the metal oxygen increased with a decrease in the crystallinity. However, the low FWHM (full width at half maximum) at the (103) plane caused by the high crystallinity depended on the increment of the oxygen vacancies at 531.66 eV due to the generation of O2. ions in the oxygen-deficient region formed by thermal activation energy.