Resonator devices are disclosed. An acoustic resonator device includes a piezoelectric plate having front and back surfaces, an acoustic Bragg reflector on the back surface, and an interdigital transducer (IDT) on the front surface. The acoustic Bragg reflector reflects a primary shear acoustic mode excited by the IDT in the piezoelectric plate over a frequency range including a resonance frequency and an anti-resonance frequency of the acoustic resonator device.