Surface acoustic wave device having an interdigital transducer provided on a main region of a piezoelectric substrate

A communication device comprising:

• at least one surface acoustic wave device including:
• a longitudinally coupled resonator filter comprising:
• a piezoelectric substrate having a pair of substrate edges and an upper surface therebetween and including a main region and a bottom surface, the piezoelectric substrate having at least one step formed therein and extending from one of said pair of substrate edges to an inner edge of the at least one step located spaced from the one of the pair of substrate edges, the inner edge of said at least one step being arranged to contact the main region and to extend from the upper surface toward the bottom surface of the piezoelectric substrate inside the one of the pair of substrate edges;
• at least two interdigital transducers provided on the main region of the piezoelectric substrate such that shear horizontal type surface acoustic waves excited by the interdigital transducer and having a wavelength of λ are reflected by the at least one inner edge;
• wherein a distance L between the inner edge of the at least one step and the corresponding one of the substrate edges is in the range of about λ/10 to about 8λ, a depth of the at least one step is in the range of about 2λ to about 6λ.

A surface acoustic wave device comprising:

• an edge reflection type longitudinally coupled resonator filter including:
• a piezoelectric substrate having a pair of substrate edges and an upper surface therebetween and including a main region and a bottom surface, the piezoelectric substrate having at least one step formed therein and extending from one of said pair of substrate edges to an inner edge of the at least one step located spaced from the one of the pair of substrate edges, the inner edge of said at least one step being arranged to contact the main region and to extend from the upper surface toward the bottom surface of the piezoelectric substrate inside the one of the pair of substrate edges;
• at least two interdigital transducers provided on the main region of the piezoelectric substrate such that shear horizontal type surface acoustic waves excited by the interdigital transducer and having a wavelength of λ are reflected by the at least one inner edge;
• wherein a distance L between the inner edge of the at least one step and the corresponding one of the substrate edges is in the range of about λ/10 to about 8λ, and a depth of the at least one step is in the range of about 2λ to about 6λ.