Elastic wave device

Abstract

Provided is an elastic wave device capable of promoting miniaturization of a filter device and capable of widening the bandwidth of a passband. This elastic wave device (10) is provided with: a piezoelectric film that includes a piezoelectric layer (14) that includes a piezoelectric body; a first comb electrode (17) that is provided on the piezoelectric layer (14), has a first bus bar (22) and a plurality of first electrode fingers (25) each having one end connected to the first bus bar (22), and is connected to an input potential; a second comb electrode (18) provided on the piezoelectric layer (14), having a second bus bar (23) and a plurality of second electrode fingers (26) each having one end connected to the second bus bar (23), and connected to the output potential, the plurality of second electrode fingers (26) and the plurality of first electrode fingers (25) being interleaved with each other; and a third electrode (19) that has a plurality of third electrode fingers (27) and connection electrodes (third bus bars (24)) that connect adjacent third electrode fingers (27) to each other, the third electrode fingers (27) being connected to a different potential from the first comb electrodes (17) and the second comb electrodes (18), the plurality of third electrode fingers (27) being provided on the piezoelectric layer (14) such that the first electrode fingers (25) and the second electrode fingers (26) are arranged in a direction in which the first electrode fingers (25) and the second electrode fingers (26) are arranged in a plan view, and the second electrode fingers (26) being arranged in a direction in which the first electrode fingers (25) and the second electrode fingers (26) are arranged in a direction in which the first electrode fingers (25) and the second electrode fingers (26) are arranged. The first electrode finger (25) and the second electrode finger (26) are aligned with each other. The order in which the first electrode fingers (25), the second electrode fingers (26), and the third electrode fingers (27) are arranged is such that the first electrode fingers (25), the third electrode fingers (27), the second electrode fingers (26), and the third electrode fingers (27) are arranged in one cycle from the first electrode fingers (25). When the longest distance between the center-to-center distance between the adjacent first electrode finger (25) and third electrode finger (27) and the center-to-center distance between the adjacent second electrode finger (26) and third electrode finger (27) is defined as p, and when the thickness of the piezoelectric film is defined as d, d / p is 0.05 or more, and p is the maximum distance between the center-to-center distance between the adjacent first electrode finger (25) and third electrode finger (27) and the center-to-center distance between the adjacent second electrode finger (26) and third electrode finger (27).