To provide a heating assembly which is used for rapid thermal processing a semiconductor substrate, hardly deteriorated in performance even when operated in a vacuum, and capable of keeping an optimal output in accordance with controlling a substrate temperature much better.

A heating assembly 12 for heating a semiconductor substrate 24 in the processing chamber 22 of a reactor 10 is equipped with a plurality of heater supports 28 and a plurality of heating devices 26 supported by the heater supports 28. The heater support 28 serves as a conductive path connecting the heating device to an outer power supply, furthermore cools down the heating device so as to keep its temperature lower than the maximum temperature, and operates the heating device at a high power. It is preferable that a cooling medium system such as a cooling medium is made to circulate at least in a part of the heater support so as to cool down the heater support and heating device.