To provide a working method of a semiconductor wafer where the grinding of a back can be executed without causing damages when thickness of the semiconductor wafer is reduced remarkably by back grinding of the semiconductor wafer, desired transfer is sufficiently easily enabled, and access to the surface of the semiconductor wafer is enabled freely after the back of the semiconductor wafer is ground, and to provide a retaining substrate to be used for the method.

Before a grinding process, the surface of the semiconductor wafer 2 is stuck on the retaining substrate 10, and the semiconductor wafer 2 is attached on the retaining substrate 10. At a time between the grinding process and the subsequent treatment process, the semiconductor wafer 2 is attached on a frame 22 where an attaching aperture 24 is formed at a central part, via an adhesive tape 20, and a transfer process is executed wherein the retaining substrate 10 is detached from the surface of the semiconductor wafer 2. The retaining substrate 10 is formed of a laminate containing a plurality of layers 14.