Boundary acoustic wave device

摘要

A boundary acoustic wave device includes an LiTaO3 piezoelectric substrate, a first dielectric medium layer disposed on the piezoelectric substrate, a second dielectric medium layer disposed on the first medium layer and having a sound velocity different from the first medium layer, and an interdigital electrode disposed at the boundary between the piezoelectric substrate and the first medium layer. The sound velocity of the first medium layer is less than the sound velocity of LiTaO3. The sound velocity of the second medium layer is greater than the sound velocity of LiTaO3. The inequality (h/λ)×a≦0.05 is satisfied, where H is the thickness of the first medium layer, h is the thickness of the interdigital electrode, λ is the period of electrode fingers of the interdigital electrode, and a is the ratio of the density of a metal of the interdigital electrode to the density of Au.

主权项

1. A boundary acoustic wave device comprising:
a piezoelectric substrate made of single-crystalline LiTaO3; a first medium layer disposed on the piezoelectric substrate and made of a dielectric material; a second medium layer disposed on the first medium layer and made of a dielectric material having a sound velocity different from a sound velocity of the dielectric of the first medium layer; and at least one interdigital electrode disposed at a boundary between the piezoelectric substrate and the first medium layer and made of a metal; wherein the sound velocity of the first medium layer is less than a sound velocity of LiTaO3, the sound velocity of the second medium layer is greater than the sound velocity of LiTaO3, and the inequality (h/λ)×a≦0.05 is satisfied, where H is the thickness of the first medium layer, h is the thickness of the interdigital electrode, λ is a period of electrode fingers of the interdigital electrode, and a is a ratio of a density of the metal defining the interdigital electrode to a density of Au, and when the LiTaO3 has Euler angles (0°±5°, θ, 0°±25°), the normalized thickness (h/λ)×a of the interdigital electrode is within one of ranges shown in Tables 16 and 17 with respect to the value of H/λ and the value of θ:TABLE 16For [0.55 ≦ H/λ < 0.65]When 0 ≦ θ < 8.5(h/λ) X a is 0.005 to 0.045.When 8.5 ≦ θ < 9.5(h/λ) X a is 0.006 to 0.045.When 9.5 ≦ θ < 10.5(h/λ) X a is 0.0115 to 0.045.When 10.5 ≦ θ < 36.5(h/λ) X a is 0.0455 to 0.045.When 36.5 ≦ θ < 37.5(h/λ) X a is 0.044 to 0.045.When 37.5 ≦ θ < 38.5(h/λ) X a is 0.026 to 0.045.When 38.5 ≦ θ < 39.5(h/λ) X a is 0.0155 to 0.045.When 39.5 ≦ θ < 40.5(h/λ) X a is 0.009 to 0.045.When 40.5 ≦ θ < 180(h/λ) X a is 0.005 to 0.045.TABLE 17For [0.65 ≦ H/λ < 0.75]When 0 ≦ θ < 7.5(h/λ) X a is 0.005 to 0.045.When 7.5 ≦ θ < 8.5(h/λ) X a is 0.005 to 0.0435.When 8.5|[M8] ≦ θ < 9.5(h/λ) X a is 0.005 to 0.0385.When 9.5 ≦ θ < 10.5(h/λ) X a is 0.009 to 0.032.When 10.5 ≦ θ < 36.5(h/λ) X a does not exist.When 36.5 ≦ θ < 37.5(h/λ) X a is 0.0305 to 0.045.When 37.5 ≦ θ < 38.5(h/λ) X a is 0.0185 to 0.045.When 38.5 ≦ θ < 39.5(h/λ) X a is 0.0105 to 0.045.When 39.5 ≦ θ < 40.5(h/λ) X a is 0.0055 to 0.045.When 40.5 ≦ θ < 180(h/λ) X a is 0.005 to 0.045.