| 摘要 |
A boundary acoustic wave device using a boundary acoustic wave propagating between a dielectric layer and LiNbO 3 or LiTaO 3 is provided. Although the boundary acoustic wave device includes a thin electrode layer, the boundary acoustic wave device has low loss using an SH-type boundary acoustic wave. A boundary acoustic wave device (1) includes a LiNbO 3 substrate (1) having a plurality of grooves (1b) formed in the upper surface thereof; electrode layers (3) which are formed by filling the grooves (1b) with a metal material and which include IDT electrodes; and a dielectric layer (4), such as a SiO 2 layer, formed over the upper surface (1b) of the piezoelectric substrate (1) and the electrodes (3). The upper surface of the dielectric layer (4) is flat. The thickness of the electrodes (3), ¸ of the Euler angles (0°, ¸, -45° to +45°) of the LiNbO 3 substrate, and the thickness of the dielectric layer (4) are within any of ranges shown in Table 1 below: [Table 1] ±‰¤0.1
¸ of Euler angles (0°, ¸, -45° to 45°) 0.04‰¤Thickness of first group electrode<0.07 (0, 76 to 106, -45 to 45) 0.8‰¤Thickness of dielectric layer‰¤2.5 0.07‰¤Thickness of first group electrode<0.1 (0, 66 to 116, -45 to 45) 0.8‰¤Thickness of dielectric layer‰¤2.5 0.1‰¤Thickness of first group electrode‰¤0.2 (0, 56 to 125, -45 to 45) 0.8‰¤Thickness of dielectric layer‰¤2.5 0.01‰¤Thickness of second group electrode<0.02 (0, 71 to 101, -45 to 45) 0.8‰¤Thickness of dielectric layer‰¤3.0 0.02‰¤Thickness of second group electrode<0.06 (0, 68 to 103, -45 to 45) 0.8‰¤Thickness of dielectric layer‰¤3.0 0.06‰¤Thickness of second group electrode<0.08 (0, 66 to 109, -45 to 45) 0.8‰¤Thickness of dielectric layer‰¤3.0 0.08‰¤Thickness of second group electrode‰¤0.16 (0, 61 to 123, -45 to 45) 0.8‰¤Thickness of dielectric layer‰¤3.0 0.01‰¤Thickness of third group electrode<0.02 (0, 61 to 112, -45 to 45) 0.8‰¤Thickness of dielectric layer‰¤4.0 0.02‰¤Thickness of third group electrode<0.06 (0, 60 to 122, -45 to 45) 0.8‰¤Thickness of dielectric layer‰¤4.0 0.06‰¤Thickness of third group electrode<0.08 (0, 56 to 132, -45 to 45) 0.8‰¤Thickness of dielectric layer‰¤4.0 0.08‰¤Thickness of third group electrode‰¤0.10 (0, 51 to 136, -45 to 45) 0.8‰¤Thickness of dielectric layer‰¤4.0 The thickness of each electrode and the thickness of a dielectric layer are normalized thickness H/» (» is the wavelength of a boundary acoustic wave).
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