With rapid development in mobile technology, film bulk acoustic resonators have developed in a highfrequency and wide bandwidth direction.This study focuses on the technological process of back cavity etching and alateral exciting film bulk acoustic resonator on the POI (LiNbO₃/SiO₂/Si).On the study of the IDT optical lithography,etching and back cavity corrosion, the critical process parameters are determined.The frequency response curveshows that resonance and antiresonance frequencies were 4 565 and 5 035 MHz, respectively.The effective electromechanicalcoupling coefficient was 20.86%, which is significant for research on high frequency and wide bandwidthfilm bulk acoustic resonators.