Surface acoustic wave device, and mobile communication device and sensor both using same

A method of manufacturing a surface acoustic wave (SAW) device, said method comprising:

• forming an electrode pattern of an inter-digital transducer (IDT) electrode prepared on a piezoelectric substrate cut out at a cut-angle allowing excitation of a leaky surface acoustic wave (LSAW), the IDT electrode having at least a pair of finger-electrodes meshing with each other;
• and
• disposing a dielectric film over the electrode pattern for covering at least the electrode pattern,
• wherein the electrode pattern, the cut-angle and a material of the dielectric film satisfy a relation of
• 2×p×fbefore≦vb≦2×p×fafter,
• where fbefore (Hz) is a resonance frequency of the SAW device before the dielectric film is formed, fafter (Hz) is a resonance frequency of the SAW device after the dielectric film is formed, p (m) is a pitch of the finger-electrodes of the electrode pattern, vb (m/s) is a phase velocity of a slow shear wave propagating on the piezoelectric substrate.

A surface acoustic wave (SAW) device comprising:

• a piezoelectric substrate cut out at a cut-angle allowing excitation of a leaky surface acoustic wave (LSAW);
• an electrode pattern formed of an inter-digital transducer (IDT) electrode prepared on said piezoelectric substrate, said IDT electrode having at least a pair of finger-electrodes meshing with each other;
• and
• a dielectric film disposed over said electrode pattern for covering at least said electrode pattern,
• wherein a pitch p (m) of said finger-electrodes satisfies a relation of 2×p×fbefore≦vb≦2×p×fafter, where f before (Hz) is a resonance frequency of said SAW device before said dielectric film is formed, fafter (Hz) is a resonance frequency of said SAW device after said dielectric film is formed, and vb (m/s) is a phase velocity of a slow shear wave propagating on said piezoelectric substrate.