In this paper, 600nm Z-cut lithium niobate (LiNbO ₃ ) thin film based third-order antisymmetric (A3) mode resonators with different geometries has been investigated. Through a series of experiments, it has been found for the first time that effective electromechanical coupling coefficient (K _eff ² ) is influenced by the gap between electrodes (Ge), and K _eff ² decreases with the increase of Ge when electrode pitch (P) higher than 5μm. Finally, a A3 mode resonator with a high 2 Keff of 6.72% is obtained. This K _eff ² is the highest reported value in similar acoustic resonators working about 9 GHz and will be beneficial to the construction of X-band filters.

As one of the core components of MEMS (i.e., micro-electro-mechanical systems), thin-film piezoelectric-on-silicon (TPoS) resonators experienced a blooming development in the past decades due to unique features such as a remarkable capability of integration for attractive applications of system-on-chip integrated timing references. However, the parasitic capacitive feedthrough poses a great challenge to electrical detection of resonance in a microscale silicon-based mechanical resonator. Herein, a fully-differential configuration of a TPoS MEMS resonator based on a novel structural design of dual interdigital electrodes is proposed to eliminate the negative effect of feedthrough. The fundamental principle of feedthrough suppression was comprehensively investigated by using FEA (i.e., finite-element analysis) modeling and electrical measurements of fabricated devices. It was shown that with the help of fully-differential configuration, the key parameter of SBR (i.e., signal-to-background ratio) was significantly enhanced by greatly suppressing the in-phase signal. The S-parameter measurement results further verified the effectiveness of this novel feedthrough suppression strategy, and the insertion loss and SBR of proposed TPoS resonators were improved to 4.27 dB and 42.47 dB, respectively.

Thin-film piezoelectric-on-silicon (TPoS) MEMS (i.e. micro-electro-mechanical system) resonators have attracted much attention due to its unique features, such as CMOS-compatible fabrication process, however, its applications require, in particular, the enhancement of quality factor ( Q ). Herein, a 10 MHz TPoS MEMS resonator with T-shaped tethers coupled with reflecting blocks was proposed. Finite-element analysis was employed for modeling the proposed TPoS resonators to investigate the underlying mechanism of Q enhancement by the introduction of T-shaped tethers and reflecting blocks. It was figured out that the combination of T-shaped tethers and reflecting blocks can significantly reduce the energy leakage through the anchor substrate by reflecting mechanical waves and trapping the energy. The measured results of fabricated TPoS resonators further verified the effectiveness of Q enhancement by the as-presented new design, and the insertion loss and the Q were improved to 3.27 dB and 1903, respectively.