| 摘要 |
PURPOSE: A thickness longitudinal piezoelectric resonator, ladder, type filter and piezoelectric resonator component is provided to suitably use for a serial arm resonator of a ladder type filter. CONSTITUTION: N-sets (N is a natural number being 3 to 5) of internal electrodes (e.g. 3 to 6) are placed in a piezoelectric body(2) of a resonator 1, and an electric field is applied alternately to piezoelectric layers among the internal electrodes 3-6 in the thickness direction in the thickness longitudinal piezoelectric resonator. In the case of N=3, a relation of (D1+D2)/2D larger or equal to 0.50 and smaller or equal to 1.00 holds, in the case of N=4, a relation of (D1+D2)/2D larger or equal to 0.50 and smaller or equal to 0.90 holds, and in the case of N=5, a relation of (D1+D2)/2D larger or equal to 0.50 and smaller or equal to 0.80 holds, where D is the thickness of the piezoelectric body between the internal electrodes adjacent in the thickness direction, and D1, D2 are the thickness of the first and second piezoelectric layers, respectively, located outside the internal electrodes that are located at outermost positions in the thickness direction.
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