A method for forming barrier layers comprises steps of providing a conductive layer, forming a first dielectric layer on the conductive layer, the first dielectric layer having a via therein, forming a first metal layer covering the first dielectric layer and the conductive layer, forming a layer of metallized materials on the first metal layer, removing the layer of metallized materials above the via bottom in the first dielectric layer, and leaving the layer of metallized materials remaining on a sidewall of the via in the first dielectric layer; and forming a second metal layer covering the layer of metallized materials. The accomplished barrier layers will have lower resistivity in the bottom via of the first dielectric layer and they are capable of preventing copper atoms from diffusing into the dielectric layer.