Owing to its high electromechanical coupling coefficient (k² _eff>30%), the horizontal shear (SH) acoustic

modes in lithium niobate (LN) single-crystal films are typically investigated to develop thin-film acoustic resonators

with large electromechanical coupling and ultra-wideband acoustic filters. However, its temperature coefficient

of frequency (TCF) is extremely high (>-50×10^-6/℃). A high TCF not only reduces the effective bandwidth

but also limits the power-management capability of the filters. Herein, we present an investigation into the

optimization design of a low drift, large electromechanical coupling horizontal-shear surface acoustic wave (SHSAW)

resonator based on the X-cut LN/SiO₂/Si structure using a threedimensional periodic finite-element model.

Simulation results show that when the SH-SAW propagation angle ψ is between -10° and -20°, the film thicknesses

of LN and SiO₂ are 0.1λ and 0.2λ (where λ is the period of the interdigital transducer) respectively, the metallization

rate of the aluminum electrode (η) is 0.4, the relative thickness of the electrode is between 5% and 10%, the k² _eff of the SH-SAW resonator remains at ~30%, and the TCF is less than -20×10^-6/℃. Hence, the resonator is

suitable for developing the next generation of low-temperature drift, ultra-wideband 5G SAW filters.