Transversely-excited film bulk acoustic resonators with interdigital transducer configured to reduce diaphragm stress

An acoustic resonator comprising:

• a substrate;
• a piezoelectric layer attached directly or via one or more intermediate layers to the substrate and having a portion that forms a diaphragm over a cavity;
• a first conductor level at a surface of the piezoelectric layer, the first conductor level including:
• first and second busbars;
• a first set of elongated fingers extending from the first busbar onto the diaphragm,
• a second set of elongated fingers extending from the second busbar onto the diaphragm, the second set of elongated fingers interleaved with the first set of elongated fingers;
• and
• a second conductor level covering at least portions of the first and second busbars,
• wherein the piezoelectric layer and the first and second sets of elongated fingers are configured such that a radio frequency signal applied between the first and second busbars excites a primary shear acoustic mode in the diaphragm.

A filter device comprising:

• a plurality of acoustic resonators, with at least one resonator of the plurality of acoustic resonators comprising:
• a substrate;
• a piezoelectric layer attached directly or via one or more intermediate layers to the substrate and having a portion that forms a diaphragm over a cavity;
• a first conductor level at a surface of the piezoelectric layer, the first conductor level including:
• first and second busbars;
• a first set of elongated fingers extending from the first busbar onto the diaphragm,
• a second set of elongated fingers extending from the second busbar onto the diaphragm, the second set of elongated fingers interleaved with the first set of elongated fingers;
• and
• a second conductor level covering at least portions of the first and second busbars,
• wherein, for the at least one acoustic resonator, the second conductor level has a thickness that is greater than a thickness of the first conductor level.