Filter device and duplexer

A filter device comprising:

• a piezoelectric substrate;
• an input terminal and an output terminal;
• a first filter section provided on the piezoelectric substrate and connected between the input terminal and the output terminal;
• and
• a second filter section provided on the piezoelectric substrate, connected between the input terminal and the output terminal, and connected in parallel to the first filter section;
• wherein
• the first filter section includes a first interdigital transducer (IDT) electrode, a first longitudinally coupled resonator-type elastic wave filter unit, a second longitudinally coupled resonator-type elastic wave filter unit cascade-connected to the first longitudinally coupled resonator-type elastic wave filter unit, and first and second inter-stage wiring lines that connect the first longitudinally coupled resonator-type elastic wave filter unit and the second longitudinally coupled resonator-type elastic wave filter unit;
• the second filter section includes a second IDT electrode, a third longitudinally coupled resonator-type elastic wave filter unit, a fourth longitudinally coupled resonator-type elastic wave filter unit cascade-connected to the third longitudinally coupled resonator-type elastic wave filter unit, and third and fourth inter-stage wiring lines that connect the third and fourth longitudinally coupled resonator-type elastic wave filter units;
• a side of the first IDT electrode is connected to the second inter-stage wiring line and a side of the second IDT electrode is connected to the third inter-stage wiring line such that phases of signals that propagate through the second and third inter-stage wiring lines are inverse to one another;
• the first filter section and the second filter section include a plurality of first terminal portions connected to a hot-side potential and a plurality of second terminal portions connected to a potential that is not the hot-side potential;
• another side of the first IDT electrode includes one of the plurality of second terminal portions of the first filter section;
• another side of the second IDT electrode includes one of the plurality of second terminal portions of the second filter section;
• and
• the filter device further includes:
• a virtual ground wiring line that connects at least one of the plurality of second terminal portions in the first filter section and at least one of the plurality of second terminal portions in the second filter section;
• a hot-side wiring portion that is adjacent to the virtual ground wiring line;
• and
• an insulating film provided on the piezoelectric substrate;
• wherein
• the hot-side wiring portion that is adjacent to the virtual ground wiring line is located on the insulating film;
• and
• the virtual ground wiring line is connected to the second terminal portion of the first IDT electrode and the second terminal portion of the second IDT electrode.