An acoustic resonator includes a piezoelectric stack including a piezoelectric layer having a top surface and a bottom surface, a top electrode layer disposed above the top surface, and a bottom electrode layer disposed below the bottom surface. A number of acoustic wave reflectors are disposed on a side of the bottom electrode layer opposite the piezoelectric layer. Each acoustic wave reflector includes a high acoustic impedance layer and may include a low acoustic impedance layer. The acoustic resonator may include a tether that extends laterally to a stacking direction of the layers of the piezoelectric stack. A supporting structure may be coupled to the tether opposite the acoustic resonator for anchoring the acoustic resonator. A mirror, one or more phononic crystals, or both may be positioned on proximate the tether opposite the acoustic resonator to avoid resonant waves from exiting the acoustic resonator in use.