Acoustic devices, structures and systems

A millimeter wave filter comprising a plurality of acoustic millimeter wave devices over a substrate, in which at least one acoustic millimeter wave device of the plurality of acoustic millimeter wave devices includes at least:

• a piezoelectric stack including at least a first piezoelectric layer and a second piezoelectric layer in which the first piezoelectric layer and the second piezoelectric layer have respective thicknesses to facilitate the at least one acoustic millimeter wave device having a main resonant frequency in a millimeter wave band;
• a top electrode;
• a bottom electrode, in which the piezoelectric stack is coupled between the top electrode and the bottom electrode, and in which the top electrode and the bottom electrode are electrically and acoustically coupled with the first piezoelectric layer and the second piezoelectric layer;
• and
• an active region associated with the piezoelectric stack, in which the active region includes at least where the top electrode and the bottom electrode overlap the first piezoelectric layer and the second piezoelectric layer to facilitate activating the at least one acoustic millimeter wave device.

A millimeter wave oscillator, comprising:

• millimeter wave oscillator circuitry;
• and
• an acoustic millimeter wave device including at least:
• a substrate;
• a piezoelectric stack including at least a first piezoelectric layer and a second piezoelectric layer in which the first piezoelectric layer and the second piezoelectric layer have respective thicknesses to facilitate the acoustic millimeter wave device having a main resonant frequency in a millimeter wave band;
• a top electrode;
• a bottom electrode, in which the piezoelectric stack is coupled between the top electrode and the bottom electrode, in which the top electrode and bottom electrode are electrically and acoustically coupled with the first piezoelectric layer and the second piezoelectric layer, and in which the millimeter wave oscillator circuitry is couple with the acoustic millimeter wave device via the top electrode and the bottom electrode;
• and
• an active region associated with the piezoelectric stack, in which the active region includes at least where the top electrode and the bottom electrode overlap the first piezoelectric layer and the second piezoelectric layer to facilitate activating the acoustic millimeter wave device.