An acoustic resonator is provided that includes a substrate; an acoustic Bragg reflector supported by the substrate; a piezoelectric plate above the acoustic Bragg reflector and opposite the substrate, the piezoelectric plate having at least one groove extending into a surface thereof; and an interdigital transducer (IDT) having a plurality of interleaved fingers with at least one finger is disposed in the at least one groove of the piezoelectric plate, respectively.