Acoustic wave device, and ladder filter including the same

An acoustic wave device comprising:

• a substrate including a piezoelectric layer;
• a first resonator on the substrate;
• a second resonator on the substrate adjacent to the first resonator and having frequency different characteristics than the first resonator;
• and
• a shared reflector on the substrate between the first resonator and the second resonator;
• wherein
• the first resonator includes a first interdigital transducer electrode including electrode fingers are positioned with a first pitch;
• the second resonator includes a second interdigital transducer electrode including electrode fingers positioned with a second pitch;
• a main mode of each of the first resonator and the second resonator is a vibration mode in which a resonant frequency decreases with an increase in a thickness of the piezoelectric layer;
• where values obtained by multiplying a pitch of electrode fingers, a duty of the electrode fingers, a thickness of the electrode fingers, and a thickness of the piezoelectric layer for the shared reflector, the first resonator, and the second resonator are respectively a fourth value, a fifth value, and a sixth value, the fourth value is the same as both the fifth value and the sixth value or between the fifth value and the sixth value;
• a higher-order mode frequency of the first resonator coincides with a higher-order mode frequency of the second resonator;
• when a number of the electrode fingers of the shared reflector is even, the electrode finger facing the shared reflector in the first interdigital transducer electrode has a same polarity as a polarity of the electrode finger facing the shared reflector in the second interdigital transducer electrode;
• and
• when the number of the electrode fingers of the shared reflector is odd, the electrode finger facing the shared reflector in the first interdigital transducer electrode has a polarity opposite to a polarity of the electrode finger facing the shared reflector in the second interdigital transducer electrode.

An acoustic wave device comprising:

• a substrate including a piezoelectric layer;
• a first resonator on the substrate;
• a second resonator on the substrate adjacent to the first resonator and having different frequency characteristics the first resonator;
• and
• a shared reflector on the substrate between the first resonator and the second resonator;
• wherein
• the first resonator includes a first interdigital transducer electrode including electrode fingers positioned with a first pitch;
• the second resonator includes a second interdigital transducer electrode including electrode fingers positioned with a second pitch;
• a main mode of each of the first resonator and the second resonator is a vibration mode in which a resonant frequency increases with an increase in a thickness of the piezoelectric layer;
• where values obtained by multiplying a pitch of electrode fingers, a duty of the electrode fingers, a thickness of the electrode fingers, and an inverse number of a thickness of the piezoelectric layer for the shared reflector, the first resonator, and the second resonator are respectively a first value, a second value, and a third value, the first value is the same as both the second value and the third value or between the second value and the third value;
• a higher-order mode frequency of the first resonator coincides with a higher-order mode frequency of the second resonator;
• when a number of the electrode fingers of the shared reflector is even, the electrode finger facing the shared reflector in the first interdigital transducer electrode has a same polarity as a polarity of the electrode finger facing the shared reflector in the second interdigital transducer electrode;
• and
• when the number of the electrode fingers of the shared reflector is odd, the electrode finger facing the shared reflector in the first interdigital transducer electrode has a polarity opposite to a polarity of the electrode finger facing the shared reflector in the second interdigital transducer electrode.