Wafer-processing sheet and method for manufacturing a semiconductor device

A method for manufacturing a semiconductor device, comprising:

• fixing a wafer-processing sheet, the wafer-processing sheet including a water-soluble resin layer formed of a water-soluble resin and a base layer formed of a resin sheet covering one side of the water-soluble resin layer and having tackiness on a surface thereof on a side toward the water-soluble resin layer under a predetermined condition, to a wafer in a plate shape, the wafer including a device region in which devices are formed and an outer peripheral excess region surrounding the device region, in an orientation such that a side of the wafer-processing sheet having the water-soluble resin layer faces the wafer;
• processing the wafer while supplying a liquid including water to the wafer;
• after the processing, separating at least the base layer of the wafer-processing sheet from the wafer;
• and
• after the separating, washing a surface of the wafer, onto which the wafer-processing sheet had been fixed, with a liquid including water.