Structures, acoustic wave resonators, devices and systems

An apparatus comprising:

• a bulk acoustic wave resonator including at least:
• a first piezoelectric layer having a first piezoelectric axis orientation;
• a second piezoelectric layer having a second piezoelectric axis orientation that substantially opposes the first piezoelectric axis orientation;
• a top acoustic reflector electrode including a first pair of top metal electrode layers electrically and acoustically coupled with the first piezoelectric layer and the second piezoelectric layer to excite a main resonant frequency of the bulk acoustic wave resonator;
• an etched edge region extending through the first piezoelectric layer, the second piezoelectric layer, and the first pair of top metal electrode layers;
• and
• electrical coupling nodes to facilitate electrical coupling of the bulk acoustic wave resonator with an oscillator circuitry.

A bulk acoustic wave resonator comprising:

• a substrate;
• a first piezoelectric layer having a first piezoelectric axis orientation;
• a second piezoelectric layer acoustically coupled to the first piezoelectric layer, the second piezoelectric layer having a second piezoelectric axis orientation that is antiparallel to the first piezoelectric axis orientation;
• and
• a top metal acoustic wave reflector electrically interfacing with the first piezoelectric layer, the top metal acoustic wave reflector including at least a first pair of top metal layers and a second pair of top metal layers, in which the first piezoelectric layer is coupled between the top metal acoustic wave reflector and the substrate.

A resonator filter comprising:

• a plurality of acoustic wave resonators, in which a first acoustic wave resonator of the plurality of acoustic wave resonators includes at least:
• a substrate;
• a first plurality of piezoelectric layers having alternating parallel and antiparallel piezoelectric axis orientations, the first plurality of piezoelectric layers having respective thicknesses, the respective thicknesses to facilitate a main acoustic resonance frequency of the first acoustic wave resonator;
• and
• a top metal acoustic wave reflector electrically interfacing with a first layer of the first plurality of piezoelectric layers, the top metal acoustic wave reflector including at least a first plurality of top metal layers and a second plurality of top metal layers, in which the first plurality of piezoelectric layers is coupled between the top metal acoustic wave reflector and the substrate.