A method of forming a contact hole includes loading a substrate into a plasma chamber, the substrate including an etch stop layer, an insulation interlayer, a mask layer and a photoresist pattern sequentially disposed thereon, applying a DC voltage to an upper electrode and applying a first high frequency power and a second high frequency power to a lower electrode to generate plasma in the chamber, the first frequency power and second high frequency powers having different frequency levels, supplying a reaction gas to the chamber to etch the mask layer and the insulation interlayer, wherein the chamber is maintained at a temperature of 100° C. to 200° C.; and etching the etch stop layer to form a contact hole