PURPOSE: To make annealing temp. considerably higher than the softening temp. of a substrate substance by supporting a substrate on a liquid having density higher than that of the substrate substance and raising the temp. of the substrate to a temp. range from the softening point of the substrate substance to the b.p. of the liquid.

CONSTITUTION: In a method and apparatus for annealing a substance such as polysilicon or the like to a substrate 7 such as a glass plate or the like, annealing temp. is set to the softening point of the substrate 7 or higher. At this time, the substrate 7 is supported on a liquid having density higher than that of the substrate 7 in order to prevent the deformation of the substrate 7. As this liquid, a molten metal or alloy having an m.p. lower than the softening point of the substrate substance is used and, for example, tin, zinc or lead is pref. Further, before the temp. of polysilicon is raised to annealing temp., a polysilicon layer 9 is protected. For example, it is pref. form a protective layer from silicon dioxide.