Longitudinal mode surface acoustic wave resonator with energy confinement layer and a method of manufacture

An apparatus comprising:

• a transceiver circuit comprising:
• a microacoustic SAW resonator, comprising:
• a substrate;
• a piezoelectric layer having a crystallographic orientation operative to excite a longitudinal mode having a resonant frequency;
• a first layer between the piezoelectric layer and the substrate and comprising a first material having a first thickness equal to or greater than a first wavelength of the longitudinal mode at the resonant frequency and a first acoustic velocity higher than a second acoustic velocity of the piezoelectric layer;
• and
• an electrode structure comprising fingers on a first surface of the piezoelectric layer;
• and
• an antenna coupled to the transceiver circuit.

A method of fabricating a microacoustic SAW resonator, the method comprising:

• forming a substrate;
• forming a piezoelectric layer having a crystallographic orientation operative to excite a longitudinal mode having a resonant frequency;
• forming a first layer between the piezoelectric layer and the substrate and comprising a first material having a first thickness equal to or greater than a first wavelength of the longitudinal mode at the resonant frequency and a first acoustic velocity higher than a second acoustic velocity of the piezoelectric layer;
• and
• forming an electrode structure comprising fingers on a first surface of the piezoelectric layer.