Elastic wave device, radio-frequency front-end circuit, and communication apparatus

An elastic wave device using an S0 mode of a plate wave, the elastic wave device comprising:

• a support substrate;
• an acoustic reflective layer laminated directly or indirectly on the support substrate;
• a piezoelectric body laminated directly or indirectly on the acoustic reflective layer;
• and
• an IDT electrode disposed directly or indirectly on the piezoelectric body;
• wherein
• the acoustic reflective layer includes:
• at least one low acoustic impedance layer with an acoustic impedance that is relatively low;
• and
• at least one high acoustic impedance layer with an acoustic impedance that is higher than the at least one low acoustic impedance layer;
• in the acoustic reflective layer, T1+T2 is between about 0.40 and about 0.60 inclusive in at least one portion in which the at least one low acoustic impedance layer is adjacent to the at least one high acoustic impedance layer in a laminating direction, where T1 is a thickness of the at least one low acoustic impedance layer and T2 is a thickness of the at least one high acoustic impedance layer, the thickness of the at least one low acoustic impedance layer being normalized by a thickness-direction component of a wavelength of a traverse bulk wave propagating in the at least one low acoustic impedance layer at an operating frequency of the elastic wave device, the thickness of the at least one high acoustic impedance layer being normalized by a thickness-direction component of a wavelength of a traverse bulk wave propagating in the at least one high acoustic impedance layer at the operating frequency of the elastic wave device;
• and
• T1/(T1+T2) is between about 0.35 and about 0.65 inclusive.