Transversely-excited film bulk acoustic resonator

A filter device, comprising:

• a substrate;
• a single-crystal piezoelectric plate having front and back surfaces, the back surface attached to the surface of the substrate, portions of the single-crystal piezoelectric plate forming one or more diaphragms spanning respective cavities in the substrate;
• and
• a conductor pattern formed on the front surface, the conductor pattern including a plurality of interdigital transducers (IDTs) of a respective plurality of acoustic resonators, interleaved fingers of each of the plurality of IDTs disposed on one of the one or more diaphragms, wherein
• the single-crystal piezoelectric plate and all of the IDTs are configured such that a respective radio frequency signal applied to each IDT excites a respective shear primary acoustic mode within the respective diaphragm, and
• each of the one or more diaphragms is contiguous with the piezoelectric plate around at least 50% of a perimeter of the respective cavity.

A method of fabricating an acoustic resonator device on a single-crystal piezoelectric plate having front and back surfaces, the back surface attached to a substrate, the method comprising:

• forming a cavity in the substrate such that a portion of the single-crystal piezoelectric plate forms a diaphragm spanning the cavity;
• and
• forming an interdigital transducer (IDT) on the front surface of the single-crystal piezoelectric plate such that interleaved fingers of the IDT are disposed on the diaphragm, the single-crystal piezoelectric plate and the IDT configured such that a radio frequency signal applied to the IDT excites a shear primary acoustic mode within the diaphragm, wherein
• the diaphragm is contiguous with the single-crystal piezoelectric plate around at least 50% of a perimeter of the cavity.