PURPOSE: To make uniform the temperature distribution on both surfaces of a semiconductor wafer by a method wherein at least the thickness of the circumferential part of one of a pair of heaters is formed thinner than the center part.

CONSTITUTION: This heater structure is composed of a pair of opposing heaters 30 arranged in a reaction chamber 32 leaving a space between them, a susceptor 34 on which a wafer 36 which is inserted between the heaters, and a susceptor supporting rod 38. Between a pair of heaters 30, the circumferential part of at least one of the heaters is thinly formed leaving the part opposing to the wafer in the center part. As resistance becomes higher on the thin part of the heaters 30, the temperature rises on the thin part, and on the contrary, the temperature of the thick part goes down. As a result, the temperature distribution on the plane of the wafer 36 can be maintained uniform even when the space between the opposing heaters becomes small, because the temperature rise in the center of the wafer 36 by the effect of the radiation from the heaters 30 can be decreased.