SUBSTRATE PROCESSING APPARATUS AND METHOD OF MANUFACTURING SEMICONDUCTOR DEVICE

PROBLEM TO BE SOLVED: To provide a substrate processing apparatus capable of reducing the risk of breaking a gas nozzle when an L-type gas nozzle is installed, with installation of the gas nozzle being easy.SOLUTION: The substrate processing apparatus includes a reaction vessel in which a plurality of substrates are stacked in Y direction for processing, a gas introducing port provided to penetrate the side wall of the reaction vessel along the X direction vertical to the Y direction, a first gas flow passage part which contains an X part extending in X direction and a Y part extending in Y direction, with the X part inserted in the gas introducing port along the X direction from inside the reaction vessel, and is provided with a first gas flow passage penetrating the X part and the Y part, a second gas flow passage part which is connected to the Y part of the first gas flow passage part in the reaction vessel, with a second gas flow passage that penetrates along Y direction being provided, a third gas flow passage part which is provided to protrude from the inside wall of the reaction vessel along the X direction, containing a third gas flow passage along Y direction, and is connected to the second gas flow passage part, and a fourth gas flow passage part which is supported by the third gas flow passage part, with a fourth gas flow passage provided along Y direction, and is provided with a gas supply opening for supplying gas to the substrate.