CPC H03H 9/02228 (2013.01) [H03H 3/04 (2013.01); H03H 9/02031 (2013.01); H03H 9/132 (2013.01); H03H 9/174 (2013.01); H03H 9/176 (2013.01); H03H 9/562 (2013.01); H03H 9/564 (2013.01); H03H 9/568 (2013.01); H03H 2003/023 (2013.01); H03H 2003/0442 (2013.01)] | 20 Claims |
1. A method of fabricating a filter device, comprising:
forming a back-side frequency setting layer on one or both of a surface of a substrate and a back surface of a piezoelectric plate;
attaching the piezoelectric plate to the substrate such that the back-side frequency setting layer is sandwiched between the surface of the substrate and the back surface of the piezoelectric plate, portions of the piezoelectric plate and backside frequency setting layer forming a plurality of diaphragms spanning a plurality of cavities, respectively, that are formed in the substrate using an etchant introduced via holes in the piezoelectric plate and back-side frequency setting layer;
forming a conductor pattern on the piezoelectric plate, the conductor pattern defining a plurality of acoustic resonators including one or more shunt resonators and one or more series resonators, each of the plurality of acoustic resonators including an interdigital transducer (IDT) formed on the piezoelectric plate with interleaved fingers on a respective diaphragm;
forming a front-side frequency setting layer over the interleaved fingers and the front surfaces of the diaphragms of the one or more shunt resonators; and
removing the back-side frequency setting layer from the back surfaces of the diaphragms of the one or more series resonators.
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