Patent ID: 7230365

Claim:
A surface acoustic wave apparatus comprising: a piezoelectric substrate including LiTaO 3 and having an electromechanical coupling coefficient that is about 15% or greater; at least one electrode provided on the piezoelectric substrate and including at least one of a metal having a density higher than Al, an alloy including a metal having a density higher than Al, a laminated film including a metal having a density higher than Al, or a laminated film including an alloy including a metal having a density higher than Al; a first insulating layer provided on the piezoelectric substrate in an area other than an area in which said at least one electrode is provided and having a thickness which substantially equals a thickness of said at least one electrode; and a second insulating layer disposed on the piezoelectric substrate to cover said at least one electrode and said first insulating layer; wherein the density of said at least one electrode is about 1.5 times or greater than the density of said first insulating layer; said piezoelectric substrate has Euler angles of about (0±3°, 115°-148°, 0±3°); said first and second insulating layers include a SiO 2 film; a normalized thickness Hs/λranges from about 0.03 to about 0.45 where Hs is a total thickness of the SiO 2 film of said first and second insulating layers and λ is a wavelength of a surface acoustic wave; the metal having a density higher than Al has a density of about 15000 to about 23000 kg/m 3 , a Young's modulus of about 0.5×10 11 to about 1.0×10 11 N/m 2 , or a transversal-wave acoustic velocity of about 1000 to about 2000 m/s; a normalized thickness H/λ ranges from about 0.013 to about 0.032 where H is a thickness of said at least one electrode and λ represents a wavelength of a surface acoustic wave; and the Euler angles (0±3°, Θ, 0±3°) of the piezoelectric LiTaO 3 substrate, the normalized thickness H/λ of said at least one electrode, and the normalized thickness Hs/λof the SiO 2 film of said first and second insulating layers are approximately equal to one of the following combinations: θ of Euler angles Electrode SiO 2 film thickness (0 ± 3°, θ, 0 ± 3°) thickness (H/λ) (Hs/λ) 120.0° ≦ θ < 123.0° 0.013–0.018 0.15–0.45 123.0° ≦ θ < 124.5° 0.013–0.022 0.10–0.40 124.5° ≦ θ < 125.5° 0.013–0.025 0.07–0.40 125.5° ≦ θ < 127.5° 0.013–0.025 0.06–0.40 127.5° ≦ θ < 129.0° 0.013–0.028 0.04–0.40 129.0° ≦ θ < 130.0° 0.017–0.030 0.03–0.42 130.0° ≦ θ < 131.5° 0.017–0.030 0.03–0.42 131.5° ≦ θ < 133.0° 0.018–0.028 0.05–0.33 133.0° ≦ θ < 135.0° 0.018–0.030 0.05–0.30 135.0° ≦ θ < 137.0° 0.019–0.032 0.05–0.25 137.0° ≦ θ ≦ 140.0° 0.019–0.032 0.05–0.25.