Abstract: An acoustic wave device includes a piezoelectric substrate and an IDT electrode including electrode fingers, a first layer on the piezoelectric substrate, and a second layer on the first layer and including Cu as a main component. The first layer includes a first principal surface on a side closest to the piezoelectric substrate and a second principal surface in contact with the second layer. The second layer includes a third principal surface in contact with the first layer, a fourth principal surface opposite to the third principal surface, and a side surface connected to the third and fourth principal surfaces. The IDT electrode includes a barrier layer on the side surface of the second layer. A boundary between the side surface of the second layer and the barrier layer is on the second principal surface of the first layer, and the barrier layer does not reach the piezoelectric substrate.

Abstract: An acoustic wave device includes a piezoelectric substrate and an IDT electrode including electrode fingers, a barrier layer on the piezoelectric substrate, and a first layer on the barrier layer, and including Cu as a main component. The first layer includes a first principal surface on a side closest to the piezoelectric substrate, a second principal surface opposite to the first principal surface, and a side surface connected to the first principal surface and the second principal surface. The barrier layer covers the first principal surface 5a and the side surface of the first layer. A thickness of a portion of the barrier layer covering the first principal surface of the first layer is smaller than a thickness of a portion of the barrier layer covering the side surface of the first layer.