PURPOSE: To suppress dusts in heat treating step by covering a heat treating plate disposed in a wafer heat treating apparatus with a heat resistance and low frictional insulating film.

CONSTITUTION: A film 9 made of heat resistance and low frictional insulating member covered on the upper surface of a first heat treating plate 5 is, for example, an ethylene tetrafluoride resin film. An aluminum plate which is treated by a hard anodic oxidation is, for example, so formed on the surface of the plate 5 that the plate 5 is rigidly covered with the film 9. Thus, a friction between a semiconductor wafer W2 and the film 9 is remarkably reduced due to the low frictional member of the film 9 between the wafer W2 and the film 9 during the passage over the plate 5 in the heat treating step, thereby largely suppressing the generation of dusts.