Transversely excited film bulk acoustic resonator using rotated Y-X cut lithium niobate

A filter device, comprising:

• a substrate;
• a lithium niobate plate having front and back surfaces, the back surface attached to the surface of the substrate, portions of the lithium niobate plate forming one or more diaphragms spanning respective cavities in the substrate;
• and
• a conductor pattern formed on the front surface, the conductor pattern including a plurality of interdigital transducers (IDTs) of a respective plurality of acoustic resonators, interleaved fingers of each of the plurality of IDTs disposed on the one or more diaphragms, wherein
• the lithium niobate plate and all of the IDTs are configured such that respective radio frequency signals applied to the IDTs excite respective primary shear acoustic modes in the respective diaphragms, and
• the Euler angles of the lithium niobate plate are [0°, β, 0° ], where β is greater than or equal to 0° and less than or equal to 60°.

A method of fabricating an acoustic resonator device, comprising:

• bonding a lithium niobate plate to a substrate such that a portion of the lithium niobate plate forms a diaphragm spanning a cavity in the substrate;
• and
• forming an interdigital transducer (IDT) on the front surface of the lithium niobate plate such that interleaved fingers of the IDT are disposed on the diaphragm, wherein
• the lithium niobate plate and the IDT are configured such that a radio frequency signal applied to the IDT excites a primary shear acoustic mode in the diaphragm, and
• the Euler angles of the lithium niobate plate are [0°, β, 0° ], where β is greater than or equal to 0° and less than 60°.