Edge reflection type surface acoustic wave device with grooves or steps at the reflection edges

A method of forming an edge reflection type surface acoustic wave device which utilizes and SH type surface acoustic wave, comprising the steps of:

• providing a surface acoustic wave substrate having a first main surface and a second main surface and first and second side surfaces;
• forming at least two interdigital transducers on the surface acoustic wave substrate;
• and
• forming a plurality of steps in the first and second side surfaces of the surface acoustic wave substrate which are located on the outer ends in the surface acoustic wave propagation direction of the surface acoustic wave substrate, the steps being positioned at an intermediate height of the first and second side surfaces, respectively, and first and second reflection edges arranged to reflect the surface acoustic wave are defined by the portions of the side surfaces located above the steps in the first and second side surfaces, respectively;
• wherein when k15 represents the electromechanical coupling coefficient of thickness shear vibration, and λ the wavelength of the surface acoustic wave, the first and second edges have a distance D between the first main surface of the surface acoustic wave substrate and each of the steps, which satisfies the following formula (2):
• 0.2≧exp (−2πk152D/λ) (2).

An edge reflection type surface acoustic wave device which utilizes an SH type surface acoustic wave, comprising:

• a surface acoustic wave substrate having a first main surface and a second main surface and first and second side surfaces;
• and
• at least two interdigital transducers provided on the surface acoustic wave substrate;
• wherein
• a plurality of steps are provided in the first and second side surfaces of the surface acoustic wave substrate which are located on the outer ends in the surface acoustic wave propagation direction of the surface acoustic wave substrate, and are positioned at an intermediate height of the first and second side surfaces, respectively, and first and second reflection edges arranged to reflect the surface acoustic wave are defined by the portions of the side surfaces located above the steps in the first and second side surfaces, respectively;
• wherein when k15 represents the electromechanical coupling coefficient of thickness shear vibration, and λ the wavelength of the surface acoustic wave, the first and second edges have a distance D between the first main surface of the surface acoustic wave substrate and each of the steps, which satisfies the following formula (2):
• 0.2≧exp (−2πk152D/λ) (2).

A method of forming an edge reflection type surface acoustic wave device comprising the steps of:

• providing a surface acoustic wave substrate having a first main surface and a second main surface;
• forming at least two interdigital transducers on the first surface of the surface acoustic wave substrate;
• and
• forming first and second grooves at opposite ends in the surface acoustic wave propagation direction of an area where said at least two interdigital transducers are provided, the first and second grooves extending from the first main surface of the surface acoustic wave substrate toward the second main surface thereof while not reaching the second main surface, the first and second grooves extending substantially perpendicularly to the surface acoustic wave propagation direction, and such that first and second edges which are arranged to reflect the surface acoustic wave are defined by inner side walls of the first and second grooves, respectively;
• wherein when k15 represents the electromechanical coupling coefficient of thickness shear vibration, and λ the wavelength of the surface acoustic wave, the first and second grooves have a depth H satisfying the following formula (1):
• 0.2≧exp (−2πk152H/λ) (1).