Method of making acoustic wave devices with multi-layer piezoelectric substrate

A method of making a radio frequency module comprising:

• forming or providing a package substrate;
• forming or providing an acoustic wave device including forming or providing a substrate with a substrate outer edge, forming or providing a functional layer over a first portion of the substrate, functional layer ending with a first tapered outer edge spaced a first distance inward from the substrate outer edge so that a second portion of the substrate is not covered by the functional layer, forming or providing a piezoelectric layer over at least a portion of the functional layer, the piezoelectric layer ending with a second tapered outer edge spaced a second distance inward from the substrate outer edge so that a second portion of the functional layer is not covered by the piezoelectric layer, a bottom of the second tapered outer edge aligned with a top of the first tapered outer edge to reduce an acoustic reflection magnitude at the second tapered outer edge of the piezoelectric layer, and forming or providing an interdigital transducer electrode over a portion of the piezoelectric layer;
• and
• attaching additional circuitry and the acoustic wave device to the package substrate.