This work presents a silicon-based capacitively transduced width extensional mode (WEM) MEMS rectangular plate resonator with quality factor (Q) of over 10,000 at a frequency of greater than 1 GHz. The Q value, determined by various loss mechanisms, was analyzed and quantified via numerical calculation and simulation. The energy loss of high order WEMs is dominated by anchor loss and phonon-phonon interaction dissipation (PPID). High-order resonators possess high effective stiffness, resulting in large motional impedance. To suppress anchor loss and reduce motional impedance, a novel combined tether was designed and comprehensively optimized. The resonators were batch fabricated based on a reliable and simple silicon-on-insulator (SOI)-based fabrication process. The combined tether experimentally contributes to low anchor loss and motional impedance. Especially in the 4th WEM, the resonator with a resonance frequency of 1.1 GHz and a Q of 10,920 was demonstrated, corresponding to the promising f × Q product of 1.2 × 1013. By using combined tether, the motional impedance decreases by 33% and 20% in 3rd and 4th modes, respectively. The WEM resonator proposed in this work has potential application for high-frequency wireless communication systems.

This work investigates the dominant loss mechanisms of the multi-frequency whispering gallery mode (WGM) resonators theoretically and experimentally, which provides a deep understanding about the working principles of the devices and guidance on their high-end applications. For the first time, the distinct AKE effects on various order WGMs were comprehensively clarified. At atmosphere, the air damping, which is conventionally expected to be negligible in high-order bulk acoustic wave (BAW) modes, is nonnegligible for all the WGMs. In vacuum, substantial Q enhancements more than 2 times were obtained. The high-order WGMs benefit more f × Q improvement from the high vacuum than the low-order ones, achieving a promising f × Q product of 1.16×1013. What’s more, the Q dynamics over a wide temperature range were characterized, which matched well with the theoretical analysis. The Akhiezer damping (AKE) is comparable with anchor loss in low-order modes, while it becomes dominated in the high-order ones. Therefore, the high-order WGMs exhibit higher Q enhancements at cryogenic temperatures. An excellent f × Q product up to 5.91×1013 was implemented at 7 K.