Substrate processing apparatus, method of manufacturing semiconductor device and non-transitory computer-readable recording medium

A substrate processing apparatus comprising:

• a reaction tube in which a plurality of substrates are accommodated;
• an inner tube provided inside the reaction tube;
• a plurality of nozzle accommodation structures provided at a side surface of the reaction tube and extending in a direction parallel to surfaces of the plurality of substrates;
• a plurality of gas supply nozzles inserted in the plurality of nozzle accommodation structures, respectively, to extend from an outside of the reaction tube to an inside of the reaction tube, and configured to supply a gas to each of the plurality of substrates such that the gas is supplied in the direction parallel to the surfaces of the plurality of substrates;
• a first gas supply structure through which a first gas is supplied to the plurality of gas supply nozzles;
• a gap provided between each of the plurality of nozzle accommodation structures and one of the plurality of gas supply nozzles corresponding thereto;
• and
• a second gas supply structure from which a second gas is supplied to the gap,
• wherein the second gas is supplied to a front end of each of the plurality of gas supply nozzles via the gap while the first gas is being supplied,
• wherein an opening is provided at a first wall surface of the inner tube at a location facing the front end of each of the plurality of gas supply nozzles, and
• wherein the front end of each of the plurality of gas supply nozzles extends toward and ends before the opening of the first wall surface of the inner tube.