Transversely-excited film bulk acoustic resonators with multiple piezoelectric membrane thicknesses on the same chip

A filter device on a single chip, the filter device comprising:

• a substrate having a surface;
• and
• a piezoelectric layer over at least one first cavity and at least one second cavity, the piezoelectric layer attached to the surface of the substrate either directly or via one or more intermediate layers, the at least one first cavity and the at least one second cavity being isolated spaces that are separated from each other;
• wherein an area of the piezoelectric layer has a first thickness for at least one first resonator that forms at least one first membrane over the at least one first cavity,
• wherein an area of the piezoelectric layer has a second thickness for at least one second resonator that forms at least one second membrane over the at least one second cavity, the second thickness being thinner than the first thickness,
• wherein at least one first interdigital transducer (IDT) is on a surface of the piezoelectric layer over the at least one first cavity and at least one second IDT is on the surface of the piezoelectric layer over the at least one second cavity, and
• wherein a bottom of the at least one first cavity that is opposite from the at least one first membrane extends farther down away from the piezoelectric layer than a bottom of the at least one second cavity that is opposite from the at least one second membrane.