Method of manufacturing semiconductor device, substrate processing apparatus and non-transitory computer-readable recording medium

A substrate processing apparatus comprising:

• a process chamber in which a substrate is processed;
• a gas supplier configured to supply an oxygen-containing gas into the process chamber;
• a heater capable of heating the substrate arranged in the process chamber;
• a plasma generator configured to excite the oxygen-containing gas supplied into the process chamber to generate a plasma;
• and
• a controller capable of controlling the gas supplier, the heater and the plasma generator to perform:
• (a) forming a first oxide layer by modifying a surface of the substrate in the process chamber at a first temperature with a plasma of a first oxygen-containing gas;
• and
• (b) forming a second oxide layer thicker than the first oxide layer by heating the substrate to a second temperature higher than the first temperature and modifying the surface of the substrate, on which the first oxide layer is formed, with a plasma of a second oxygen-containing gas.