A damascene structure includes a conductive layer, a first dielectric layer, a first barrier metal layer, a barrier layer, and a second barrier metal layer sequentially formed on the conductive layer. The first dielectric layer having a via therein. The barrier layer is comprised of a material different with that of the first barrier metal layer. A bottom of the barrier layer disposed on the via bottom is not punched through. The accomplished barrier layers will have lower resistivity on the via bottom in the first dielectric layer and they are capable of preventing copper atoms from diffusing into the dielectric layer.