Solidly-mounted transversely-excited film bulk acoustic filters with multiple piezoelectric plate thicknesses

A filter device comprising:

• a piezoelectric layer having a first portion having a first thickness and a second portion having a second thickness less than the first thickness;
• and
• a conductor pattern on the first portion and the second portion of the piezoelectric layer, the conductor pattern comprising:
• a first interdigital transducer (IDT) with interleaved fingers on the first portion, and
• a second IDT with interleaved fingers on the second portion,
• wherein the first IDT is a part of a first shunt resonator and the second IDT is a part of a first series resonator in a ladder filter circuit of the filter device,
• wherein at least a portion of interleaved fingers of the second IDT has a width that is greater than 0.2 times a pitch of the second IDT and less than 0.3 times the pitch of the second IDT, and
• wherein the pitch of the interleaved fingers of the second IDT is a center-to-center spacing between two adjacent interleaved fingers of the second IDT that extend from different busbars of the second IDT.

A filter device comprising:

• a piezoelectric layer having a first portion that has a first thickness and a second portion that has a second thickness less than the first thickness;
• an acoustic multilayer reflector attached to the piezoelectric layer;
• a first interdigital transducer (IDT) with interleaved fingers on the first portion of the piezoelectric layer;
• and
• a second IDT with interleaved fingers on the second portion of the piezoelectric layer,
• wherein the first IDT is a part of a first shunt resonator and the second IDT is a part of a first series resonator in a ladder filter circuit of the filter device,
• wherein at least a portion of interleaved fingers of the second IDT has a width that is greater than 0.2 times a pitch of the second IDT and less than 0.3 times the pitch of the second IDT, and
• wherein the pitch of the interleaved fingers of the second IDT is a center-to-center spacing between two adjacent interleaved fingers of the second IDT that extend from different busbars of the second IDT.