In this study, we investigate the dispersive behavior of the electromechanical coupling coefficient ( [Formula: see text]) for shear-horizontal (SH) and Rayleigh surface acoustic wave (SAW) modes in a YX-LiNbO3 (LN)/SiO2/Si substrate across various wavelengths. Due to the difference in velocity dispersion between the SH and Rayleigh modes, mode coupling can be observed when these two modes operate at closely proximate frequencies, leading to a notable variation in their [Formula: see text]. With a careful design, SH and Rayleigh modes can be tuned to achieve a mode-decoupling state for enhancing [Formula: see text] of the SH-SAW and suppressing the presence of the Rayleigh mode in YX-LN/SiO2/Si. Consequently, a series of proof-of-concept SH-SAW resonators with wavelengths ( λ ) ranging from 1.6 to [Formula: see text] are fabricated. The optimized resonator with a λ of [Formula: see text] exhibits a resonant frequency of 1.064 GHz, an effective [Formula: see text] of 47.7%, a maximum Bode- Q of around 900, and an 18-dB rejection of spurious modes spanning from 0.5 to 3 GHz, without the presence of the Rayleigh mode.