Patent ID: 7569413

Claim:
A method for forming a thin film structure, which includes a lower film and an upper film, on a substrate, comprising: a step of forming the lower film that includes a polysilicon film on the substrate, a step of making the lower film to be conductive by doping an impurity into the lower film and thermally diffusing the impurity, a step of forming the upper film that includes a second polysilicon film on the lower film, the upper film being nonconductive and having a first tensile stress in approximately a same level as a compressive stress of the lower film, and a step of separating the thin film structure from the substrate by a first etching, leaving at least a part of a periphery of the thin film structure held by the substrate, wherein the thin film structure as a whole is adjusted to have a final tensile stress, and wherein after the impurity is doped into the lower film, an anti-defect film is formed on a top of the lower film before the impurity is thermally diffused.