Acoustic resonator

An acoustic resonator, comprising:

• a plurality of stacked layers comprising:
• a piezoelectric layer having a first surface and a second surface on opposite sides thereof;
• a first electrode layer disposed above the first surface;
• and
• a second electrode layer disposed below the second surface;
• and
• a plurality of first acoustic wave reflectors disposed on a side of the second electrode layer opposite the piezoelectric layer,
• wherein each of the first acoustic wave reflectors comprises a first acoustic impedance layer having a first acoustic impedance value (Za) at least as great as 60×106 N·s/m3,
• wherein at least one of the first acoustic wave reflectors comprises a second acoustic impedance layer, the second acoustic impedance layer having a second acoustic impedance value (Zb) and being disposed on a side of an adjacent one of the first acoustic impedance layer opposite the second electrode layer, and
• wherein a first absolute value of a difference between the first and second acoustic impedance values (Za, Zb) is at least as great as 40% of a second absolute value of a sum of the first and second acoustic impedance values (Za, Zb).

An acoustic resonator, comprising:

• a plurality of stacked layers comprising:
• a piezoelectric layer having a first surface and a second surface on opposite sides thereof;
• a first electrode layer disposed above the first surface;
• and
• a second electrode layer disposed below the second surface;
• a plurality of first acoustic wave reflectors disposed on a side of the second electrode layer opposite the piezoelectric layer, each of the first acoustic wave reflectors comprising a first acoustic impedance layer having a first acoustic impedance (Za) at least as great as 60×106 N·s/m3;
• at least one supporting structure coupled to and disposed laterally to a stacking direction of the stacked layers;
• at least one tether coupling at least one side or at least one end of the stacked layers to the at least one supporting structure;
• and
• at least one second acoustic wave reflector associated with at least one of (i) the at least one supporting structure and (ii) the at least one tether, the at least one second acoustic wave reflector being configured to reflect acoustic waves.