Elastic wave device and method for manufacturing the same

An elastic wave device comprising:

• a supporting substrate;
• an acoustic reflection layer on the supporting substrate;
• a piezoelectric layer on the acoustic reflection layer;
• and
• an IDT electrode on an upper or lower surface of the piezoelectric layer, the piezoelectric layer being thinner than a period of fingers of the IDT electrode;
• wherein
• the acoustic reflection layer includes a low-acoustic-impedance layer and a high-acoustic-impedance layer having a higher acoustic impedance than an acoustic impedance of the low-acoustic-impedance layer;
• the low-acoustic-impedance layer is made of SiO2, and the high-acoustic-impedance layer is made of at least one material selected from the group consisting of W, LiTaO3, AI2O3, AIN, LiNbO3, SiN, and ZnO;
• the piezoelectric layer is made of LiNbO3 or LiTaO3;
• Euler Angles of the LiNbO3 of the piezoelectric layer are (0, 20, 0) to (0, 50, 0), (90, 90, 25) to (90, 90, 44), or (0, 95, 0) to (0, 132, 0);
• or
• Euler Angles of the LiTaO3 of the piezoelectric layer are (0, 12, 0) to (0, 48, 0), (90, 90, 13) to (90, 90, 36), or (0, 100, 0) to (0, 134, 0).