Resonator devices and filter devices are disclosed. An acoustic resonator includes a substrate and a piezoelectric plate having front and back surfaces separated by a piezoelectric plate thickness greater than or equal to 50 nm and less than or equal to 200 nm. An acoustic Bragg reflector is between the substrate and the back surface of the piezoelectric plate. A conductor pattern including an interdigital transducer (IDT) is on the front surface of the piezoelectric plate.