| 摘要 |
<p>Provided is an acoustic wave device having a small temperature coefficient of frequency (TCF), a small insertion loss, and a large electromechanical coupling coefficient and capable of increasing an electrode finger pitch. The acoustic wave device (1) comprises a piezoelectric body (10), an IDT electrode (30), and a dielectric layer (20) covering the IDT electrode (30). The dielectric layer (20) has a temperature coefficient of frequency with a sign opposite to or equal to the sign of the temperature coefficient of frequency of the piezoelectric body (10) and having an absolute value smaller than the absolute value of the temperature coefficient of frequency of the piezoelectric body (10). The IDT electrode (30) includes electrode fingers (31b, 32b) having a first electrode layer (21) and a second electrode layer (22). The first electrode layer (21) is positioned inside a groove (10a). The second electrode layer (22) is positioned above the upper end surface of the groove (10a). A value of (?3 × C44)1/2 of the first electrode layer (21) is greater than a value of (?3 × C44)1/2 of the second electrode layer (22).</p> |
