Workpiece treating method, semiconductor device, process for manufacturing the same, and temporary fixing composition for shear peeling

A workpiece treating method comprising:

• a step (1) of forming a stack including a support, a temporary fixing material and a workpiece, wherein the temporary fixing material includes a layer containing a polymer (A) in a range of not less than 50 mass %, the polymer (A) including a structural unit represented by the following formula (A1), and the workpiece is held on the temporary fixing material;
• a step (2) of processing the workpiece and/or transporting the stack;
• and
• a step (3) of applying a shear force to the temporary fixing material to thereby separate the workpiece from the support,
• wherein in the formula (A1), R1 is a divalent organic group including at least one aromatic ring, each of two oxygen atoms bonded to R1 in the formula (A1) is bonded to the aromatic ring, and, when R1 includes two or more aromatic rings, each of the two oxygen atoms is bonded to any one of the aromatic rings.