The growing demand for high-performance frequency control and power conversion systems has intensified research interest in piezoelectric MEMS resonators. This thesis investigates three piezoelectric material systems, including aluminum nitride (AlN), aluminum scandium nitride (AlScN), and lithium niobate (LiNbO₃), operating in different acoustic modes: bulk acoustic wave (BAW), thickness shear (TS), and Lamb wave modes, By co-designing piezoelectric materials, resonator geometries, and acoustic modes, this work aims to develop high-performance resonators for ultra-stable clocks, wideband RF filtering, and energy-efficient power converters.

In the first project, a temperature-compensated AlN BAW resonator is integrated with a micro-oven and temperature sensor, allowing the device temperature to be actively controlled near its turnover temperature and thereby reducing temperature-induced frequency drift while preserving a high Q for stable timing applications. In the second project, AlScN Lamb-wave resonators are designed in the radial-extension mode, where in-plane strain components constructively enhance the piezoelectric response and produce higher electromechanical coupling than conventional length- and width-extension modes. In the third project, LiNbO₃ thickness-shear resonators employ asymmetric lateral shape engineering to disrupt lateral standing waves and suppress spurious modes, enabling a clean resonance spectrum with high electromechanical coupling and high Q for piezoelectric power conversion.