Acoustic wave device and multiplexer

An acoustic wave device comprising:

• a support substrate including silicon and having a plane orientation of (110);
• a piezoelectric layer directly or indirectly provided on the support substrate and in which rotated Y-cut X-propagation lithium tantalate is included;
• and
• an IDT electrode including a plurality of electrode fingers and provided on the piezoelectric layer;
• wherein
• a film thickness of the piezoelectric layer is less than or equal to about 1λ, where λ is a wavelength defined by an electrode finger pitch of the IDT electrode;
• and
• when (XLT, YLT, ZLT) are crystal axes of the lithium tantalate of the piezoelectric layer, k110 is a directional vector obtained by projecting the ZLT axis onto the (110) plane of the support substrate, α110 is an angle between the directional vector k110 and a [001] direction of the silicon of the support substrate, and n is an arbitrary integer (0, ±1, ±2, . . . ), the angle α110 is in a range of about 0°+180°×n≤α110≤40°+180°×n or in a range of about 140°+180°×n≤α110≤180°+180°×n.

An acoustic wave device comprising:

• a support substrate including silicon and having a plane orientation of (100);
• a piezoelectric layer directly or indirectly provided on the support substrate and in which rotated Y-cut X-propagation lithium tantalate is provided;
• and
• an IDT electrode including a plurality of electrode fingers and provided on the piezoelectric layer;
• wherein
• a film thickness of the piezoelectric layer is less than or equal to about 1λ, where λ is a wavelength defined by an electrode finger pitch of the IDT electrode;
• and
• when (XLT, YLT, ZLT) are crystal axes of the lithium tantalate of the piezoelectric layer, k100 is a directional vector obtained by projecting the ZLT axis onto the (100) plane of the support substrate, α100 is an angle between the directional vector k100 and a [001] direction of the silicon of the support substrate, and n is an arbitrary integer (0, ±1, ±2, . . . ), the angle α100 is in a range of about 20°+90°×n≤α100≤70°+90°×n.