A method of forming a suspension object on a monolithic substrate is provided. A silicon base layer of the monolithic substrate has a circuit layer composed of at least one wet etching region, at least one circuit region, and at least one microstructure region. The wet etching region is used to partition the circuit region and the microstructure region, and extends downwards to a surface of the silicon base layer, so as to form an etching path for etching the silicon base layer from above the substrate. Next, an upper surface and a lower surface of the silicon base layer are respectively etched through dry etching, such that the microstructure region is suspended.