US Patent 11791794 Transversely-excited film bulk acoustic resonator with reduced spurious modes

Acoustic filters, resonators and methods of making acoustic filters are disclosed. An acoustic resonator device includes a substrate. A back surface of a piezoelectric plate is attached to the substrate, a portion of the piezoelectric plate forming a diaphragm that spans a cavity in the substrate. A conductor pattern is formed on the front surface of the piezoelectric plate, the conductor pattern including an interdigital transducer (IDTs) with interleaved fingers of the IDT disposed on the diaphragm. A ratio of the mark of the interleaved fingers to the pitch of the interleaved fingers is greater than or equal to 0.2 and less than or equal to 0.3.