Performance improvement of saw resonator by selectively changing amount of materials

A surface acoustic wave (SAW) resonator, comprising:

• a piezoelectric structure;
• an interdigital transducer (IDT) residing over the piezoelectric structure, such that portions of the piezoelectric structure are exposed through the IDT, wherein:
• the IDT comprises a plurality of first electrode fingers and a plurality of second electrode fingers extending in a transverse direction;
• the plurality of first electrode fingers and the plurality of second electrode fingers are interleaved with one another along a longitudinal direction orthogonal to the transverse direction;
• and
• the IDT has at least one edge region that extends in the longitudinal direction and spans across certain ones of the plurality of first electrode fingers and certain ones of the plurality of second electrode fingers, wherein an acoustic wave propagates in the at least one edge region at a different velocity than other regions confined in the IDT;
• and
• a passivation structure at least partially covering the IDT and the exposed surfaces of the piezoelectric structure, wherein the at least one edge region is realized in the IDT by at least one thickness variation of a thickness variation of the piezoelectric structure and a thickness variation of the passivation structure.