Semiconductor substrate having multilayer film and method to reuse the substrate by delaminating a porous layer

A method for producing a semiconductor wafer having a multilayer film, in production of a semiconductor device by the steps of forming a porous layer on a surface of a semiconductor wafer by changing a surface portion of the semiconductor wafer into the porous layer, forming a semiconductor film on a surface of the porous layer to produce the semiconductor wafer having a multilayer film, fabricating a device on the semiconductor film, and producing the semiconductor device by delaminating the semiconductor film along the porous layer, the semiconductor film having the device formed thereon;

• comprising at least:
• flattening a surface of a porous layer side of the semiconductor wafer after delaminating the semiconductor film having the device formed thereon, the porous layer being used for the delamination, and
• reusing the flattened semiconductor wafer as the semiconductor wafer for forming the porous layer to perform the steps of forming the porous layer and of forming the semiconductor film;
• the method further comprising a thickness adjusting step of adjusting a whole thickness of the semiconductor wafer having a multilayer film to be produced by reusing the semiconductor wafer so as to satisfy a predetermined standard, wherein
• a number of reuse for the flattened semiconductor wafer is set to at least 3 times or more, and
• the thickness adjusting is performed by adjusting a thickness of the semiconductor film to be formed on the surface of the porous layer only after forming the porous layer on the surface of the reused semiconductor wafer.