[Object] To provide an interconnection structure and a method of forming the same, the interconnection structure capable of avoiding an increase in leakage current or an increase in interconnection resistance caused by oxidation, being less likely to have electromigration occur therein, and having a higher reliability than the conventional ones. [Solving Means] After a copper interconnection is formed above a substrate, a surface of the copper interconnection is activated by performing acid cleaning. Thereafter, the substrate is immersed in a BTA (Benzo triazole) aqueous solution to form a protection film covering the surface of the copper interconnection. At this time, Cu-N-R bonds (R is an organic group) are formed in grain boundary portions in the surface of the copper interconnection. Thereafter, the protection film is removed by performing alkaline cleaning. The Cu-N-R bonds remain in the grain boundary portions in the surface of the copper interconnection even after the protection film is removed. Subsequently, the surface of the copper interconnection is subjected to an activation process, and a barrier layer is formed thereafter by electroless-plating the surface of the copper interconnection with NiP or CoWP.