Piezoresistive microphone and method of fabricating the same

A fabricating method of a piezoresistive microphone, comprising:

• providing a substrate and an insulating layer covering the substrate;
• forming an amorphous silicon layer to cover the insulating layer;
• crystallizing the amorphous silicon layer to become a first polysilicon layer;
• forming a second polysilicon layer to cover the first polysilicon layer;
• forming a first resistor within the second polysilicon, wherein the steps of forming the first resistor comprise:
• forming a plurality of first lightly doped regions within the second polysilicon layer;
• and
• forming a plurality of first heavily doped regions in the second polysilicon layer, wherein the first lightly doped regions connect to the first heavily doped regions;
• forming two conductive pads on the polysilicon layer and electrically connecting to the first resistor;
• etching the first polysilicon layer and the second polysilicon layer simultaneously to form a first pattern and a second pattern, wherein the first resistor is disposed between the first pattern and the second pattern;
• and
• etching the substrate and the insulating layer to form a cavity.