Abstract: The present invention relates to insulating layers and a forming method thereof, more particularly, to planarized insulating layers among wires on the same insulating layer or different layers and a forming method thereof which minimize parasitic capacitance generated from the wires, prevent via poison and reduce step difference between the adjacent layers by forming a dielectric layer having a low dielectric constant between the wires patterned in the same layer and by forming an insulating interlayer having excellent heat-dissipation efficiency and interface-adhesiveness between the wires in the different layer.