Spurious Modes Suppression in Lithium Niobate Lamb Mode Resonators by SiO2-embedded Electrode Design

This work proposes a spurious mode suppression strategy for lithium niobate (LiNbO3) first-order antisymmetric (A1) Lamb wave resonators by silicon dioxide (SiO2)-embedded electrode design. Traditional XBAR resonators suffer from higher-order spurious modes due to acoustic impedance mismatch between metallized and non-metallized regions. To address this, we introduce an SiO2 layer between interdigital transducers (IDTs) to balance the equivalent acoustic parameters of adjacent regions. Analytical modeling and finite-element method (FEM) simulations demonstrate that the SiO2 layer aligns the dispersion curves of metallized and non-metallized zones, thereby mitigating boundary reflections and suppressing spurious modes. The design achieves a spurious mode suppressed response, offering a practical pathway to enhance the performance and reliability of high-frequency A1-mode resonators for radio-frequency applications.