Crystalline Y-cut Lithium Niobate Layers for the Bulk Acoustic Wave Resonator (YBAR)

The film bulk-acoustic wave resonator (FBAR) technology based on aluminum nitride (AIN) thin films has proven very successful, but it is limited by the relatively low piezoelectric coupling of AIN. Recently, FBAR resonators and laterally excited standing wave resonators (XBARs) using shear waves have been demonstrates on rotated Y-cut lithium niobate (LiNbO3) thin films. Here we propose one more device of this type, “YBAR”, where the rotated Y-cut lithium niobate membrane is between an IDT-like structure of electrodes on the one side and a single solid floating electrode on the back side. The device has an extremely large resonance-anti-resonance distance up to 22%, corresponding to coupling coefficient K2 ~ 60%, promising for design of wideband ladder-type filters for 5G. The structure is also suitable for surface mounted resonator (SMR) configuration.