A substrate processing apparatus and a method of manufacturing a semiconductor device, the apparatus including a plasma region in which plasma is generated; a processing region in which a substrate is processable; a shower head including a first channel and a second channel, the first channel being a passage through which the plasma flows between the plasma region and the processing region and the second channel being a passage through which a process gas is supplied to the processing region, the first channel and the second channel being separated from each other; a substrate support supporting the substrate in the processing region; and a cooler configured to supply a cooling fluid to a cooling channel of the substrate support.