Bulk acoustic wave resonant structure and preparation method therefor, and acoustic wave device

A preparation method of a bulk acoustic wave resonance structure, comprising:

• providing a substrate, and forming a sacrificial layer on a surface of the substrate;
• etching the sacrificial layer to remove a part of the sacrificial layer to form first grooves;
• filling a first electrode material in the first grooves;
• forming a first electrode covering the first electrode material, the sacrificial layer, and the substrate;
• wherein the first electrode comprises a first sub-electrode located in a first region and second sub-electrodes located in a second region outside the first region;
• etching the first electrode to remove a part of the first electrode to form second grooves;
• wherein the second grooves expose a part of the first electrode material;
• filling a sacrificial material in the second grooves;
• forming a piezoelectric layer covering the sacrificial material and the first electrode;
• forming a second electrode on a side, remote from the substrate, of the piezoelectric layer;
• wherein the piezoelectric layer in the first region is in direct contact with the first sub-electrode and the second electrode;
• forming at least one etch hole penetrating through the piezoelectric layer, removing the sacrificial material through the at least one etch hole to form first gaps, and removing the sacrificial layer through the at least one etch hole to form a reflection structure;
• wherein each of the first gaps is located between the piezoelectric layer and a respective one of the second sub-electrodes, and an orthographic projection of the first gap on the substrate is located around the first region.

A preparation method of a bulk acoustic wave resonance structure, comprising:

• providing a substrate, and forming a sacrificial layer on a surface of the substrate;
• forming first electrode material protrusions on the substrate;
• wherein each of the first electrode material protrusions covers a part of a sidewall of the sacrificial layer;
• forming a first electrode covering the first electrode material protrusions, the sacrificial layer and the substrate;
• wherein the first electrode comprises a first sub-electrode located in a first region and second sub-electrodes located in a second region outside the first region;
• etching the first electrode to remove a part of the first electrode to form second grooves;
• filling a sacrificial material in the second grooves;
• forming a piezoelectric layer covering the sacrificial material and the first electrode;
• forming a second electrode on a side, remote from the substrate, of the piezoelectric layer;
• wherein the piezoelectric layer in the first region is in direct contact with the first sub-electrode and the second electrode;
• forming at least one etch hole penetrating through the piezoelectric layer, removing the sacrificial material through the at least one etch hole to form first gaps, and removing the sacrificial layer through the at least one etch hole to form a reflection structure;
• wherein each of the first gaps is located between the piezoelectric layer and a respective one of the second sub-electrodes, and an orthographic projection of the first gap on the substrate is located around the first region.