Elastic wave device, duplexer, and multiplexer

An elastic wave device comprising:

• a piezoelectric substrate;
• a first longitudinally coupled resonator elastic wave element on the piezoelectric substrate including:
• a first plurality of interdigital transducer (IDT) electrodes;
• a first reflector on a first side in an elastic wave propagation direction of a portion where the first plurality of IDT electrodes are located;
• and
• a second reflector disposed on a second side in the elastic wave propagation direction of the portion where the first plurality of IDT electrodes are located;
• a second longitudinally coupled resonator elastic wave element that is aligned or substantially aligned with the first longitudinally coupled resonator elastic wave element along the elastic wave propagation direction on the piezoelectric substrate, the second longitudinally coupled resonator elastic wave element including:
• a second plurality of IDT electrodes;
• a third reflector disposed on a first side in the elastic wave propagation direction of a portion where the second plurality of IDT electrodes are located;
• and
• a fourth reflector disposed on a second side in the elastic wave propagation direction of the portion where the second plurality of IDT electrodes are located;
• and
• a ground interconnection included on the piezoelectric substrate and electrically connected to the first and second longitudinally coupled resonator elastic wave elements;
• wherein
• the second reflector and the third reflector are adjacent to or in a vicinity of each other in the elastic wave propagation direction;
• the ground interconnection extends in a direction intersecting with the elastic wave propagation direction and in a region between the second reflector and the third reflector;
• the ground interconnection includes a different acoustic velocity portion with an acoustic velocity different from an acoustic velocity in a remaining portion of the ground interconnection, the different acoustic velocity portion being located in a region between the second reflector and the third reflector and overlapping with an elastic wave propagation region of the first and second longitudinally coupled resonator elastic wave elements when viewed in the elastic wave propagation direction;
• and
• the ground interconnection includes a first interconnection layer that is continuously connected to the second reflector and the third reflector and that fills the region between the second reflector and the third reflector.