Method of fabricating transversely-excited film bulk acoustic resonator

A method of fabricating a filter device, comprising:

• fabricating an acoustic resonator chip, comprising:
• attaching a back surface of a piezoelectric plate to a substrate such that portions of the piezoelectric plate form a plurality of diaphragms spanning respective cavities in the substrate;
• and
• forming a first conductor pattern on a front surface of the piezoelectric plate, the first conductor pattern comprising:
• a plurality of interdigital transducer (IDT) of a corresponding plurality of acoustic resonators, interleaved fingers of each IDT on a respective diaphragm from the plurality of diaphragms, and
• a first plurality of contact pads;
• forming a second conductor pattern on a back surface of an interposer, the second conductor pattern comprising:
• a second plurality of contact pads;
• attaching the back surface of the interposer to the front surface of the piezoelectric plate by directly bonding each contact pad of the first plurality of contact pads to a respective contact pad of the second plurality of contact pads;
• and
• forming a seal between a perimeter of the acoustic resonator chip and a perimeter of the interposer.