An interconnection element of an interconnection structure of an integrated circuit is manufactures by a method where a cavity is etched in an insulating layer. A silicon nitride layer is then deposited on walls and a bottom of the cavity. The nitrogen atom concentration in the silicon nitride layer increasing as a distance from an exposed surface of the silicon nitride layer increases. A copper layer is deposited on the silicon nitride layer. The cavity is further filled with copper. A heating process is performed after the deposition of the copper layer, to convert the copper layer and the silicon nitride layer to form a copper silicide layer which has a nitrogen atom concentration gradient corresponding to the gradient of the silicon nitride layer.