Bulk acoustic wave device including frame outside of active region and flat bottom piezoelectric layer

A bulk acoustic wave device having an active region, the bulk acoustic wave device comprising:

• an acoustic reflector;
• electrodes including a first electrode and a second electrode;
• and
• a piezoelectric layer having a recess outside of the active region, the first electrode positioned between the piezoelectric layer and the acoustic reflector in the active region, the piezoelectric layer having a surface facing the acoustic reflector that is planar (a) over an entirety of the active region and (b) beyond the first electrode over the acoustic reflector, the first electrode and the second electrode overlapping and being on opposing sides of the piezoelectric layer in the active region.

An acoustic wave filter for filtering a radio frequency signal, the acoustic wave filter comprising:

• a bulk acoustic wave resonator including an acoustic reflector;
• electrodes including a first electrode and a second electrode;
• a piezoelectric layer having a surface facing the acoustic reflector that is flat (a) over an entirety of an active region of the bulk acoustic wave resonator and (b) beyond the first electrode over the acoustic reflector, the first electrode and the second electrode overlapping and being on opposing sides of the piezoelectric layer in the active region, and the first electrode positioned between the piezoelectric layer and the acoustic reflector in the active region;
• and a frame structure over the acoustic reflector;
• and
• a plurality of additional acoustic wave resonators, the bulk acoustic wave resonator and the plurality of additional acoustic wave resonators configured to filter the radio frequency signal.