Acoustic wave device and manufacturing method for acoustic wave device

An acoustic wave device comprising:

• a support substrate with a thickness in a first direction;
• a piezoelectric layer above or below the support substrate;
• and
• a functional electrode on the piezoelectric layer;
• wherein
• a space is provided between the support substrate and the piezoelectric layer and at least partially overlaps the functional electrode in a plan view in the first direction;
• at least one through-hole extends through the piezoelectric layer and communicates with the space;
• the at least one through-hole is provided inside an outer edge of the space in a plan view in the first direction;
• and
• in a plan view in the first direction, at least a portion of an outer edge of the through-hole is provided along the outer edge of the space and is a section in which a distance to the outer edge of the space is constant or substantially constant.

A manufacturing method for an acoustic wave device, the manufacturing method comprising:

• preparing a support substrate and a piezoelectric layer including a first principal surface and a second principal surface on an opposite side to the first principal surface, laminating an intermediate layer in which a sacrificial layer is embedded, on the second principal surface of the piezoelectric layer, and bonding the piezoelectric layer and the support substrate with the intermediate layer interposed between the piezoelectric layer and the support substrate;
• after the preparing, forming at least a functional electrode and a first portion of a support portion;
• after the forming at least the functional electrode and the first portion of the support portion, forming a through-hole in the piezoelectric layer at a position that overlaps the sacrificial layer in a lamination direction of the support substrate and the piezoelectric layer in a plan view, causing an etchant to enter the sacrificial layer via the through-hole, and forming a first cavity portion by removing the sacrificial layer;
• preparing a lid substrate and forming a second portion of the support portion in the lid substrate;
• and
• after the forming the first cavity portion and the preparing the lid, forming a second cavity portion between the functional electrode and the lid substrate by joining the first portion of the support portion with the second portion of the support portion;
• wherein
• the support substrate has a thickness in a first direction;
• and
• in a plan view in the first direction, the first cavity portion includes an extended passage having a smaller area than a region overlapping the functional electrode, and the through-hole is provided inside an outer edge of the extended passage.