Method of manufacturing a semiconductor device and substrate processing apparatus

A substrate processing apparatus comprising:

• a processing chamber configured to receive a substrate having an oxide film and a nitride film stacked thereon;
• a substrate support member provided in the processing chamber, the substrate support member configured to support and heat the substrate;
• a gas flow rate controller configured to adjust flow rates of hydrogen-containing gas and nitrogen-containing gas in a process gas;
• a gas supplying unit configured to supply the process gas into the processing chamber,
• a plasma generator configured to excite the process gas;
• and
• a control unit configured to control the substrate support member, the gas flow rate controller, the gas supplying unit and the plasma generator,
• wherein the control unit controls the substrate support member to heat the substrate carried in the processing chamber, controls the gas flow rate controller to adjust the flow rates of hydrogen-containing gas and nitrogen-containing gas such that a percentage R of the number of hydrogen atoms with respect to the total number of hydrogen atoms and nitrogen atoms in the process gas is set to be 0%<R≦80%, controls the gas supplying unit to supply the process gas with the adjusted flow rates into the processing chamber, and controls the plasma generator to excite the process gas supplied into the processing chamber and process the substrate with the excited process gas.