Transversely-excited film bulk acoustic resonator with a cavity having round end zones

An acoustic resonator device comprising:

• a piezoelectric layer including a portion that forms a diaphragm over a cavity of the acoustic resonator device;
• and
• an interdigital transducer (IDT) on a surface of the piezoelectric layer, the IDT including interleaved fingers that extend from a pair of busbars,
• wherein the interleaved fingers of the IDT are over at least a portion of the piezoelectric layer that forms a diaphragm over a cavity of the acoustic resonator device,
• wherein the cavity includes a perimeter defined in a plan view of the piezoelectric layer, and the diaphragm is the portion of the piezoelectric layer that is within the perimeter of the cavity, and
• wherein the perimeter of the cavity includes at least one rounded corner that has a portion that overlaps the at least one busbar of the pair of busbars in the plan view of the piezoelectric layer.

A filter device, comprising:

• a plurality of bulk acoustic resonators, with at least one of the bulk acoustic resonators including:
• a substrate;
• a piezoelectric layer attached to the substrate, wherein at least a portion of the piezoelectric layer is disposed over a cavity of the acoustic resonator device;
• and
• an interdigital transducer (IDT) on a surface of the piezoelectric layer, the IDT including interleaved fingers extending at least over the portion of the piezoelectric layer disposed over the cavity,
• wherein the cavity has at least one rounded corner, and
• wherein a portion of interleaved fingers extend from at least one busbar,
• wherein at least a portion of the rounded corner of the cavity is under the at least one busbar in a plan view of the piezoelectric layer.