Substrate processing apparatus and method of manufacturing semiconductor device

A substrate processing apparatus comprising:

• a process chamber in which a substrate is processed;
• two process gas nozzles arranged substantially in parallel with a gap therebetween, and configured to supply a process gas into the process chamber;
• a first inert gas nozzle and a second inert gas nozzle fluidly coupled to an inert gas supply, the first and second inert gas nozzles provided respectively in two regions divided by a first straight line passing through the gap between the two process gas nozzles and a center of the substrate, and configured to supply inert gas into the process chamber, wherein an angle between the first straight line and a second straight line extending from the center of the substrate to each of the first and second inert gas nozzles is within a range from 90 to 180 degrees;
• an exhaust port configured to exhaust an inner atmosphere of the process chamber;
• and
• a controller configured to control a first flow rate of inert gas through the first inert gas nozzle and a second flow rate of inert gas through the second inert gas nozzle so that a concentration of the process gas at the center of the substrate is higher than a concentration of the process gas circumferentially averaged at an edge of the substrate when the process gas from the two process gas nozzles and the inert gas from the first and second inert gas nozzles flow over the substrate.