The invention provides a semiconductor structure and a forming method thereof. The forming method comprises the steps of providing a semiconductor substrate; forming an interlayer dielectric layer on the semiconductor substrate and performing nitrogen ion treatment on the surface of the interlayer dielectric layer; etching the interlayer dielectric layer to form a contact hole; filling metallic copper in the contact hole to form a copper interconnecting wire; forming a silicon-rich silicon nitride layer, wherein the silicon-rich silicon nitride layer covers the copper interconnecting wire and the interlayer dielectric layer; forming a copper barrier layer, wherein the copper barrier layer covers the silicon-rich silicon nitride layer. By performing the nitrogen ion treatment on the surface of the interlayer dielectric layer, the adhesion between the interlayer dielectric layer and the silicon-rich silicon nitride layer is improved accordingly, and further the adhesion between the interlayer dielectric layer and the copper barrier layer is improved, the stripping problem is avoided, and the reliability of an integrated circuit is improved.