Acoustic wave device including multiple regions with multiple acoustic velocities

An acoustic wave device comprising:

• a support substrate;
• a piezoelectric film made of lithium tantalate or lithium niobate;
• a high acoustic velocity material layer made of at least one material selected from a group including aluminum nitride, aluminum oxide, silicon nitride, and DLC film;
• a low acoustic velocity material layer made of silicon oxide;
• and
• an interdigital transducer electrode that is provided on the piezoelectric film;
• wherein
• the high acoustic velocity material layer, the low acoustic velocity material layer, and the piezoelectric film are stacked in this order on the support substrate;
• the interdigital transducer electrode includes a first busbar and a second busbar that oppose each other, multiple first electrode fingers each of which includes a base end that is connected to the first busbar and a tip end that extends toward the second busbar, and multiple second electrode fingers each of which includes a base end that is connected to the second busbar and a tip end that extends toward the first busbar;
• the multiple first electrode fingers and the multiple second electrode fingers overlap in an overlapping region in a direction in which an acoustic wave propagates, and the overlapping region includes a central region, a first edge region that is located between the central region and the first busbar, and a second edge region that is located between the central region and the second busbar;
• an acoustic velocity in the first edge region and an acoustic velocity in the second edge region are lower than an acoustic velocity in the central region;
• the first busbar and the second busbar are provided in a busbar region, and an acoustic velocity in the busbar region is higher than the acoustic velocity in the central region;
• and
• a first region is between the first edge region and the first busbar, a second region is between the second edge region and the second busbar, and an acoustic velocity in a portion of the second region and the first region is lower than the acoustic velocity in the busbar region.

An acoustic wave device comprising:

• a piezoelectric film made of lithium tantalate or lithium niobate;
• a high acoustic velocity support substrate made of at least one material selected from a group including sapphire, crystal, silicon carbide, and silicon;
• a low acoustic velocity material layer made of silicon oxide;
• and
• an interdigital transducer electrode that is provided on the piezoelectric film;
• wherein
• the low acoustic velocity material layer and the piezoelectric film are stacked in this order on the high acoustic velocity support substrate;
• the interdigital transducer electrode includes a first busbar and a second busbar that oppose each other, multiple first electrode fingers each of which includes a base end that is connected to the first busbar and a tip end that extends toward the second busbar, and multiple second electrode fingers each of which includes a base end that is connected to the second busbar and a tip end that extends toward the first busbar;
• the multiple first electrode fingers and the multiple second electrode fingers overlap in an overlapping region in a direction in which an acoustic wave propagates, and the overlapping region includes a central region, a first edge region that is located between the central region and the first busbar, and a second edge region that is located between the central region and the second busbar;
• an acoustic velocity in the first and second edge regions is lower than an acoustic velocity in the central region;
• an acoustic velocity in a busbar region in which the first busbar and the second busbar are provided is higher than the acoustic velocity in the central region;
• and
• a first region is between the first edge region and the first busbar, a second region is between the second edge region and the second busbar, and an acoustic velocity in a portion of the second region and the first region is lower than the acoustic velocity in the busbar region.