A formation method of a semiconductor structure comprises the steps of providing a substrate in which a bottom-layer metal layer is formed; forming a dielectric layer covering the surfaces of the substrate and the bottom-layer metal layer, wherein the material of the dielectric layer has a porous structure; forming a patterned mask layer on the surface of the dielectric layer; taking the patterned mask layer as a mask to etch the dielectric layer, forming an opening penetrating the dielectric layer, and exposing the top surface of the bottom-layer metal layer out of the bottom of the opening; adopting a carbon-containing gas to carry out the first etching postprocessing on the opening, and forming a sealing layer on the surface of the side wall of the opening; after the sealing layer is formed, adopting a wet etching process to etch and remove the patterned mask layer; forming a conductive layer filling the opening, wherein the top of the conductive layer is parallel and level with the top of the dielectric layer. According to the present invention, a technical window for forming the conductive layer is added, and the electrical property of the semiconductor structure is improved.