| Popis: |
Provided is an elastic boundary-wave device capable of suppressing a high-order mode spuriousness effectively with a relatively simple structure. In the elastic boundary-wave device (1), an IDT electrode (5) is arranged in the boundary between a piezoelectric element (2) and a dielectric element (3), and a low thermal-expansion coefficient medium layer (4) made of a material having a smaller linear thermal expansion coefficient than that of the piezoelectric element (2) is laminated on the side, as opposed to the boundary, of the piezoelectric element (2). The sound velocity of a transverse wave in an elastic boundary-wave propagating direction in the piezoelectric element (2), the dielectric element (3) and the low thermal-expansion coefficient medium layer (4) satisfies the following formula (1), and the sound-velocity/λ of the transverse wave in the dielectric element satisfies the following formula (2), when the IDT electrode (5) has a wavelength λ. The sound velocity of the transverse wave in the dielectric element < the sound velocity of an SH wave in the dielectric element < the sound velocity of the transverse wave in the low thermal-expansion coefficient medium layer m Formula (1), and The response frequency of the elastic boundary wave < the sound-velocity/λ of the transverse wave in the dielectric element < the response frequency of the high-order mode m Formula (2). |
