In this paper, the piezoelectric ZnO micro membranes were fabricated and investigated as biosensor platform. This membrane device was fabricated by MEMS technology from ZnO thin film deposited by megnetron sputtering. The vibration behaviors of membranes in different sizes were analyzed using scanning Mach-Zehnder interferometer. The resonance frequencies and vibration modes were got and the mass sensitivities were calculated. The results show that the ZnO device works like membrane and could be considered as a good candidate of biosensor platform. The stress of the membrane structure was calculated and the results indicate a potential application that membrane could also be used to monitor the stress during the thin film deposition. (C) 2011 Elsevier B.V. All rights reserved.