Suppression of Transverse Modes in 50°YX-LiTaO₃/SiO₂/Si POI SAW Resonator with Groove Configuration

With the rapid development of mobile communication technology, the POI (piezoelectric on insulator) structure has gained recognition in the field of RF filtering. However, transverse modes remain in the passband of corresponding surface acoustic wave (SAW) devices, which impedes their application in crowded spectra. This article introduces a groove configuration to suppress transverse modes for POI SAW resonators employing a 50°YX-LiTaO 3 /SiO 2 /Si multilayered structure. First, the response of conventional POI SAW resonators was calculated by the 3D periodic FEM method, and the results indicate that transverse modes caused by energy leakage to busbar regions are serious in POI SAW resonators. Then, the groove configuration was adopted to confine energy within the aperture region by reducing the velocity at the end of IDT electrodes, and the groove dimension was optimized to achieve a nearly spurious-free response in the passband. Finally, experimental results of fabricated one-port SAW resonators with optimal groove configuration were provided to validate the suppression of transverse modes and the enhancement of the Q factor in the POI SAW resonator.