A conductive interconnect structure includes a contact pad; a conductive body connected to the contact pad at a first end; and a conductive layer positioned on a second end of the conductive body. The conductive body has a longitudinal direction perpendicular to a surface of the contact pad. The conductive body has an average grain size (a) on a cross sectional plane (Plane A) whose normal is perpendicular to the longitudinal direction of the conductive body. The conductive layer has an average grain size (b) on Plane A. The conductive body and the conductive layer are composed of same material, and the average grain size (a) is greater than the average grain size (b).