Elastic wave device and method for producing the same

An elastic wave device configured to use an SH surface acoustic wave comprising:

• a lithium niobate film;
• a supporting substrate;
• a high-acoustic-velocity film located on the supporting substrate and configured so that an acoustic velocity of a propagating bulk wave is higher than an acoustic velocity of an elastic wave that propagates on the lithium niobate film;
• a low-acoustic-velocity film stacked on the high-acoustic-velocity film and configured so that an acoustic velocity of a propagating bulk wave is lower than an acoustic velocity of a bulk wave that propagates in the lithium niobate film, the lithium niobate film being stacked on the low-acoustic-velocity film;
• and
• an IDT electrode located on either side of the lithium niobate film;
• wherein
• when the lithium niobate film has Euler angles of (0°±5°, θ, 0°), the Euler angle θ is in a range of about 0° to about 8° and about 57° to about 180°.

A method for producing an elastic wave device, the method comprising:

• providing a supporting substrate;
• forming a high-acoustic-velocity film on the supporting substrate, the high-acoustic-velocity film being configured so that an acoustic velocity of a propagating bulk wave is higher than an acoustic velocity of an elastic wave that propagates on lithium niobate;
• forming a low-acoustic-velocity film on the high-acoustic-velocity film, the low-acoustic-velocity film being configured so that an acoustic velocity of a propagating bulk wave is lower than an acoustic velocity of a bulk wave that propagates in lithium niobate;
• forming a lithium niobate film on the low-acoustic-velocity film, the lithium niobate film being configured so that θ of Euler angles (0°±5°, θ, 0°) is in a range of about 0° to about 8° or about 57° to about 180°;
• and
• forming an IDT electrode on either side of the lithium niobate film.