In recent years, as further reduction in price and higher performance have been required of semiconductor devices, higher productivity in a film forming process of a wafer and higher quality, such as improved evenness in film thickness, have also been required.
To meet such requirements, backside heating is employed using a single epitaxial film forming apparatus in which, for example, a wafer rotating at a high speed of 900 rpm or above in a reaction chamber is heated from the backside using a heater configured with a resistive heat generating body while a process gas is supplied into the reaction chamber.
In such epitaxial film forming apparatus, reduction in the heat capacity of a heater is required to improve thermal responsiveness. One idea to reduce the heat capacity of the heater is to make the heater thinner, but a turnover portion should be widen to adjust the electrical resistance to a desired value.
However, a current does not flow evenly in the heater element but concentrates at the turnover portion. The current concentration causes breakage at the turnover portion, which disadvantageously shortens the life of a heater.