A method for fabricating a microstructure is to form at least one insulation layer including a micro-electro-mechanical structure therein over an upper surface of a silicon substrate. The micro-electro-mechanical structure includes at least one microstructure and a metal sacrificial structure that are independent with each other. In the metal sacrificial structure are formed a plurality of metal layers and a plurality of metal via layers connected to the respective metal layers. A barrier layer is formed over an upper surface of the insulation layer, and an etching stop layer is subsequently formed over a lower surface of the silicon substrate. An etching operation is carried out from the lower surface of the silicon substrate to form a space corresponding to the micro-electro-mechanical structure, and then the metal sacrificial structure is etched, thus achieving a microstructure suspension.