Semiconductor device manufacturing method and substrate manufacturing method of forming silicon carbide films on the substrate

A semiconductor device manufacturing method comprising:

• (a) loading a plurality of substrates stacked at predetermined intervals into a reaction chamber;
• (b) forming silicon carbide films on the plurality of substrates by:
• supplying, as a source gas, at least a silicon-containing gas free of hydrogen atoms and a chlorine-containing gas free of hydrogen atoms or at least a gas containing silicon and chlorine and free of hydrogen atoms into the reaction chamber from a first gas supply outlet of a first gas supply unit configured to supply a gas in a direction parallel to main surfaces of the plurality of substrates disposed in the reaction chamber,
• supplying, as a reducing gas, at least a hydrogen gas or a hydrogen-containing gas into the reaction chamber from a second gas supply outlet of a second gas supply unit, and
• supplying at least a carbon-containing gas into the reaction chamber from the first gas supply outlet of the first gas supply unit or the second gas supply outlet of the second gas supply unit while controlling the first gas supply unit and the second gas supply unit in a manner that a ratio of chlorine to hydrogen supplied into the reaction chamber is smaller than a predetermined value;
• and
• (c) etching an inside of the first gas supply unit by controlling the first gas supply unit in a manner that the ratio of chlorine to hydrogen inside the first gas supply unit is greater than the predetermined value.