Miniature LiNbO3/SiO2/Si SH-SAW Resonators with Near-Spurious-Free Response

In this letter, we present an investigation into the design, simulation, and characterization of near-spurious-free shear horizontal surface acoustic wave (SH-SAW) resonators that utilize a short acoustic aperture (A) in a LiNbO₃/SiO₂/Si functional substrate. By forming a miniature design through reducing the aperture of the interdigital transducer (IDT) from 20 wavelengths (&null) to only 2&null, we observed a significant reduction in the transverse resonance of the guided SH-SAW, while still retaining the maximum Bode-Q ( Q_max ). The proposed miniature resonators exhibit an excellent Q_max of 1,200 and an electromechanical coupling (k ² _eff) of 25% at 1 GHz with thin gold (Au) electrodes. These properties led to a high figure-of-merit (FoM_max = k ² _eff &null Q_max) of 300. Using this technique, GHz SH-SAW resonators with miniaturized transducer capacitance C_o down to 160 fF are also characterized with a high FoM_max &null 200. The implementation of such miniature resonators holds significant promise for emerging applications that demand a near-spurious-free response and scalable capacitance, such as RF impedance transformers and low power oscillators for ultra-low-power radios.