In a method of cutting a wafer, a supporting member is attached to an upper surface of the wafer on which semiconductor chips are formed. An opening is formed at a lower surface of the wafer along a scribe lane of the wafer. The lower surface of the wafer may be plasma-etched to reduce a thickness of the wafer. A tensile tape may be attached to the lower surface of the wafer. Here, the tensile tape includes sequentially stacked tensile films having different tensile modules. The supporting member is then removed. The tensile tape is cooled to increase the tensile modules between the tensile films. The tensile tape is tensed until the tensile films are cut using the tensile modules difference to separate the tensile tape from the semiconductor chips. Thus, the lower surface of the wafer may be plasma-etched without using an etching mask.