Piezoelectric device including piezoelectric body layer with positive and negative polarization charges

A piezoelectric device comprising:

• a base portion including a first main surface and a second main surface located opposite to the first main surface, the base portion including an opening provided in the first main surface;
• and
• a layered portion layered on a side of the first main surface of the base portion, the layered portion covering the opening from above;
• wherein
• the layered portion includes, at least above the opening, a first single-crystal piezoelectric body layer, a second single-crystal piezoelectric body layer above the first single-crystal piezoelectric body layer, an intermediate electrode layer between the first single-crystal piezoelectric body layer and the second single-crystal piezoelectric body layer, a lower electrode layer on a lower side of the first single-crystal piezoelectric body layer and opposed to the intermediate electrode layer with the first single-crystal piezoelectric body layer being interposed, and an upper electrode layer on an upper side of the second single-crystal piezoelectric body layer and opposed to the intermediate electrode layer with the second single-crystal piezoelectric body layer being interposed, and the layered portion includes a membrane portion which is a portion that covers the opening;
• the layered portion is provided with a hole that reaches the lower electrode layer through the first single-crystal piezoelectric body layer, the intermediate electrode layer, and the second single-crystal piezoelectric body layer at a position on an outer side of the opening when viewed in a direction orthogonal to the first main surface;
• a drawn electrode connected to the lower electrode layer and insulated from the intermediate electrode layer inside of the hole and drawn to an upper surface of the second single-crystal piezoelectric body layer is provided;
• the first single-crystal piezoelectric body layer includes a material that produces a difference in etching rate between a positive side and a negative side of a polarization charge;
• and
• the polarization charge of the first single-crystal piezoelectric body layer is positive on a side of the intermediate electrode layer and negative on a side of the lower electrode layer.