| CPC H03H 9/1092 (2013.01) [H01L 23/02 (2013.01); H01L 23/04 (2013.01); H03H 9/02897 (2013.01); H03H 9/02937 (2013.01); H03H 9/02984 (2013.01); H03H 9/059 (2013.01); H03H 9/1071 (2013.01); H03H 9/25 (2013.01); H03H 9/6483 (2013.01)] | 20 Claims |

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1. An electronic device, comprising:
a piezoelectric substrate including a first main surface;
a functional element provided on or above the first main surface;
an insulation material layer provided on or above the first main surface and surrounding the functional element; and
a protective layer provided on or above the insulation material layer; wherein
the piezoelectric substrate and the insulation material layer define a hollow portion that accommodates the functional element;
in a cross-sectional view in a direction perpendicular to a thickness direction of the piezoelectric substrate, the protective layer includes:
a first portion above the hollow portion;
a second portion adjacent to the first portion at one end of the second portion; and
a third portion adjacent to the second portion at another end of the second portion;
a direction parallel to the first main surface is a first direction in the cross-sectional view in the direction perpendicular to the thickness direction of the piezoelectric substrate; and
a maximum distance in the first direction between one end portion and another end portion of the protective layer is less than a maximum distance in the first direction between one end portion and another end portion of the piezoelectric substrate.
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