The recent adoption of lithium niobate (LiNbO3)-based acoustic filters for 5G front ends, driven by their exceptional electromechanical coupling ( k2eff ) and frequency scalability, has established LiNbO3 thin films as a compelling platform for next-generation communication systems. However, the large temperature coefficient of frequency (TCF) inherent to this material remains an open challenge limiting the deployment of these resonators in applications requiring high frequency stability. This work proposes a locally buried SiO2 architecture to achieve temperature compensation in thickness-excited LiNbO3 thin-film bulk acoustic resonators (FBARs). Sub-wavelength SiO2 regions are embedded within the LiNbO3 thin film, enabling efficient thermal compensation while preserving large k2eff values. Y-cut LiNbO3 thickness-shear FBARs incorporating the proposed architecture are fabricated, demonstrating a TCF improvement from −118 ppm/°C to −39ppm/°C for the most compensated designs, while retaining more than 20% electromechanical coupling at moderate compensation levels. The measured results show good agreement with finite element simulations, confirming the validity of the compensation mechanism. This work demonstrates a viable path toward wideband temperature-stable LiNbO3 FBAR filters for future wireless communication systems. [2026-0133]