Baw structure having multiple baw transducers over a common reflector, which has reflector layers of varying thicknesses

A Bulk Acoustic Wave (BAW) device comprising:

• a substrate comprising a planar surface;
• a first reflector over the substrate and comprising a first plurality of reflector layers;
• a first BAW transducer over a first section of the first reflector that is over the planar surface of the substrate and comprising a first piezoelectric layer of a first thickness between a first top electrode and a first bottom electrode;
• and
• a second BAW transducer over a second section of the first reflector that is over the planar surface of the substrate and comprising a second piezoelectric layer of a second thickness between a second top electrode and a second bottom electrode, wherein:
• the first thickness is different than the second thickness;
• in the first section of the first reflector beneath the first BAW transducer, a first average thickness of each of the first plurality of reflector layers is approximately one-quarter the wavelength (λ/4) of a first acoustic wave for a frequency at which a first acoustic mode of a first type operates in the first BAW transducer and a second acoustic wave for a second frequency at which a second acoustic mode of a second type operates;
• in the second section of the first reflector beneath the second BAW transducer, a second average thickness of each of the first plurality of reflector layers is approximately one-quarter the wavelength (λ/4) of a third acoustic wave for a frequency at which the first acoustic mode of the first type operates in the second BAW transducer and a fourth acoustic wave for a fourth frequency at which the second acoustic mode of the second type operates;
• and
• the first average thickness is different than the second average thickness.