Substrate processing apparatus and method of manufacturing semiconductor device

A substrate processing apparatus comprising:

• an outer tube;
• a manifold connected to the outer tube, the manifold being made of a non-metal material;
• an inner tube disposed on the manifold at a more inner side than the outer tube and configured to process a substrate therein;
• a heating device installed at a more outer side than the outer tube and configured to heat an inside of the outer tube;
• a lid configured to open and close an opening of the manifold with a seal member intervened between the lid and the manifold;
• and
• a press member configured to press a bottom end of the inner tube,
• wherein a guard part is disposed at a lower outer side of the inner tube,
• wherein the manifold comprises:
• an inner tube placement part having the inner tube placed thereon;
• a protrusion part disposed at a more outer periphery than the inner tube placement part and higher than a height of the guard part with respect to the inner tube placement part;
• and
• a groove part installed at a more outer periphery than the protrusion part, and
• wherein one end of the press member is inserted into the protrusion part, and the other end of the press member is inserted into the groove part.