Microphone device based on two-dimensional piezoelectric material layer having protective layer formed thereon, and method for fabricating the same

A method for manufacturing a microphone device based on a two-dimensional piezoelectric material layer having a protective layer formed thereon, the method comprising:

• preparing a substrate;
• forming a lower protective layer on an upper surface of the substrate, wherein a plurality of surface structures, each having an upwardly gradually narrower shape, are arranged on the lower protective layer;
• forming a two-dimensional piezoelectric material layer on the lower protective layer in a conformal manner to the plurality of surface structures of the lower protective layer such that a pre-strain is applied to the two-dimensional piezoelectric material layer;
• forming an upper protective layer on the two-dimensional piezoelectric material layer;
• forming at least one electrode;
• and
• etching a lower surface of the substrate so as to form a cavity vertically extending through the substrate,
• wherein the microphone device is configured to generate an electric potential as the two-dimensional piezoelectric material layer vibrates under a sound pressure.