FIGURE 9.

Schematic of a typical acoustic resonators. (a) Bulk acoustic wave (BAW) resonator, where acoustic waves propagate vertically through the entire 3D structure of the piezoelectric material following electrical field application. (b) Surface acoustic wave (SAW) resonator, composed of a comb‐shaped interdigital transducer (IDT) on a piezoelectric material. When an AC voltage is applied to the IDT, acoustic waves are generated, which are confined to the substrate surface (Rayleigh waves) and perpendicular to the IDT