Method of making packaged acoustic wave devices with multilayer piezoelectric substrate

A method of making a radio frequency module comprising:

• forming or providing a package substrate;
• forming or providing a packaged acoustic wave component including an acoustic wave device including forming or providing a substrate, forming or providing a dielectric layer over at least a portion of the substrate, forming or providing a piezoelectric layer over at least a portion of the dielectric layer, forming or providing one or more signal lines including forming or providing a first signal line that extends over a first end of the piezoelectric layer and forming or providing a second signal line that extends over a second end of the piezoelectric layer opposite the first end, each of the first and second signal lines including a first portion recessed in the substrate and a second portion of the piezoelectric layer, the first portion recessed in the substrate having a top surface that is below the dielectric layer, and attaching a thermally conductive metal structure to both the substrate and the one or more signal lines, the one or more signal lines interconnecting the piezoelectric layer and the thermally conductive metal structure, the thermally conductive metal structure being spaced from the piezoelectric layer so an outer edge of the piezoelectric layer is spaced inward of an inner surface of the thermally conductive metal structure, the thermally conductive metal structure covering the piezoelectric layer to form a cavity over the piezoelectric layer, and forming or providing a polyimide layer on a surface of the thermally conductive metal structure so that the polyimide layer is on an inside of the cavity opposite the piezoelectric layer;
• and
• attaching additional circuitry and the packaged acoustic wave component to the package substrate.