Methods of forming metal lines in semiconductor devices are disclosed. One example method may include forming lower metal lines and forming an insulation layer on the lower metal lines; etching said insulation layer to a depth; and depositing a material for upper metal lines on the entire surface of said insulation layer and planarizing the material for the upper metal lines to form said upper metal lines. The example method may also include exposing the lower metal lines by etching said upper metal lines and the insulation layer and depositing a material for contact plugs on the entire surfaces of said upper metal lines and said insulation layer and planarizing the material for said contact plugs to form the contact plugs.