Acoustic wave device

An acoustic wave device, comprising:

• a piezoelectric layer;
• and
• a first electrode and a second electrode facing each other in a direction intersecting a thickness direction of the piezoelectric layer;
• wherein
• the acoustic wave device utilizes a bulk wave in a thickness-shear primary mode;
• a material of the piezoelectric layer is lithium niobate or lithium tantalate;
• at least a portion of each of the first electrode and the second electrode is embedded in the piezoelectric layer;
• about 0.048≤d/p≤about 0.072, where in a cross-section along the thickness direction of the piezoelectric layer, an inter-centerline distance between the first electrode and the second electrode is denoted as p, and a thickness of the piezoelectric layer is denoted as d;
• the first electrode and the second electrode are adjacent to each other;
• the first electrode includes a first electrode main portion intersecting the second electrode in the direction in which the first electrode and the second electrode face each other;
• the second electrode includes a second electrode main portion intersecting the first electrode in the direction in which the first electrode and the second electrode face each other;
• the piezoelectric layer includes a defined region in the piezoelectric layer which intersects both the first electrode and the second electrode in the direction in which the first electrode and the second electrode face each other and is between the first electrode and the second electrode in a plan view from the thickness direction of the piezoelectric layer;
• and
• in a plan view from the thickness direction of the piezoelectric layer, when an area of the first electrode main portion is denoted as S1, an area of the second electrode main portion is denoted as S2, an area of the defined region is denotes as S0, and a structural parameter defined by (S1+S2)/(S1+S2+S0) is denoted as MR, the acoustic wave device satisfies a condition of MR≤1.75×(d/p)+0.075.