| 摘要 |
PROBLEM TO BE SOLVED: To provide a surface wave device with a piezoelectric film formed on a crystal substrate, having less spurious with satisfactory temperature characteristics and can enlarge the electro-mechanical coupling coefficient K<SP>2</SP>of the Rayleigh wave. SOLUTION: The surface wave device 1 comprises the crystal substrate 2 which has Euler angles (ϕ,θ,ψ), whereϕis in the range of -2.5°±5°,θis in the range of 116°±5°, andψis in the range of +2.5°±5°, the piezoelectric film 5 formed on the crystal substrate 2, and interdigital electrodes 3a, 3b, 4a and 4b formed to be brought into contact with the piezoelectric film 5. When the Euler angles of the crystal substrate 2 are within the ranges which allow a power flow angle PFA of the Rayleigh wave in FIG. 6 to be±2.5°, and allow the frequency temperature coefficient TCF of the surface wave device in FIG. 7 to be±5 ppm/°C, the thickness of the film 5 is defined as H, and if the wavelength of a surface wave isλ, the standardized film thickness H/λof the piezoelectric film 5 will be 0.05 or larger and the frequency temperature coefficient TCF of the piezoelectric film 5 has a negative value. COPYRIGHT: (C)2007,JPO&INPIT
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