Multilayer piezoelectric substrate device with modified interdigital transducer structure to improve insertion loss

A radio frequency (RF) ladder filter comprising:

• a set of series resonators connected in series between an input and an output of the RF ladder filter, the set of series resonators including at least one of a first type of acoustic wave device, the first type of acoustic wave device including a carrier substrate, a layer of dielectric material having a lower surface disposed against an upper surface of the carrier substrate, a layer of piezoelectric material having a lower surface disposed against an upper surface of the layer of dielectric material, a pair of interdigital transducer electrodes disposed on an upper surface of the layer of piezoelectric material, each interdigital transducer electrode including a bus bar, and a plurality of electrode fingers extending from the bus bar to distal ends of the electrode fingers at an edge region of the interdigital transducer electrode, and trench portions located in the upper surface of the layer of piezoelectric material, said trench portions being overlapped by the edge regions of the interdigital transducer electrodes, the electrode fingers having a uniform width;
• and
• a set of parallel resonators connected in parallel between the acoustic wave devices of the set of series resonators and ground in a shunt configuration, the set of parallel resonators including at least one of a second type of acoustic wave device, the second type of acoustic wave device including a carrier substrate, a layer of dielectric material having a lower surface disposed against an upper surface of the carrier substrate, a layer of piezoelectric material having a lower surface disposed against an upper surface of the layer of dielectric material, a pair of interdigital transducer electrodes disposed on an upper surface of the layer of piezoelectric material, each interdigital transducer electrode including a bus bar, and a plurality of electrode fingers extending from the bus bar to distal ends of the electrode fingers at an edge region of the interdigital transducer electrode, and trench portions located in the upper surface of the layer of piezoelectric material, said trench portions overlapping with the edge regions of the interdigital transducer electrodes, the electrode fingers having regions at their distal ends that have a reduced width, the reduced width region having lengths of between about 1.1λ and 1.2λ, where λ is the wavelength of the acoustic wave to be generated.

An electronics module comprising at least one radio frequency filter that includes at least one acoustic wave device, the at least one acoustic wave device including:

• a carrier substrate;
• a layer of dielectric material having a lower surface disposed against an upper surface of the layer of carrier substrate;
• a layer of piezoelectric material having a lower surface disposed against an upper surface of the layer of dielectric material;
• a pair of interdigital transducer electrodes disposed on an upper surface of the layer of piezoelectric material, each interdigital transducer electrode including a bus bar and a plurality of electrode fingers extending from the bus bar to distal ends of the electrode fingers at an edge region of the interdigital transducer electrode;
• and
• trench portions located in the upper surface of the layer of piezoelectric material, said trench portions being overlapped by the edge regions of the interdigital transducer electrodes, the electrode fingers having regions at their distal ends that have a reduced width, the reduced width regions having a length of between about 1.1λ and 1.2λ, where λ is the wavelength of the acoustic wave to be generated.