| CPC H03H 9/17 (2013.01) [H03H 3/02 (2013.01); H03H 9/02157 (2013.01); H03H 9/133 (2013.01); H03H 9/568 (2013.01); H03H 2003/023 (2013.01)] | 13 Claims |

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1. A bulk acoustic wave resonator comprising a membrane including a piezoelectric film having an odd number of more than two layers of piezoelectric material, a centermost of the more than two layers of piezoelectric material having a higher doping level than others of the more than two layers of piezoelectric material.
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