Bulk acoustic wave resonators with patterned mass loading layers

An acoustic wave die comprising:

• a first bulk acoustic wave resonator on the bulk acoustic wave die, the first bulk acoustic wave resonator including a first patterned mass loading layer having a first density, the first patterned mass loading layer impacting a resonant frequency of the second bulk acoustic wave resonator;
• and
• a second bulk acoustic wave resonator on the bulk acoustic wave die, the second bulk acoustic wave resonator including a second patterned mass loading layer having a second density, the second density being higher than the first density, the second patterned mass loading layer impacting a resonant frequency of the second bulk acoustic wave resonator.

A radio frequency module comprising:

• an acoustic wave filter including a first bulk acoustic wave resonator and a second bulk acoustic wave resonator, the first bulk acoustic wave resonator including a first patterned mass loading layer having a first density and impacting a resonant frequency of the first bulk acoustic wave resonator, the second bulk acoustic wave resonator including a second patterned mass loading layer having a second density, the second density being higher than the first density, and the second patterned mass loading layer, the second patterned mass loading layer impacting a resonant frequency of the second bulk acoustic wave resonator;
• and
• a radio frequency circuit element coupled to an acoustic wave filter that includes at least the first bulk acoustic wave resonator, the acoustic wave filter and the radio frequency circuit element being enclosed within a common module package.