Substrate processing apparatus and furnace opening cover

A reaction container comprising:

• a furnace opening unit formed at a bottom portion of the reaction container and comprising an upper surface, an inner circumferential surface with inward projections and a lower surface;
• and
• a furnace opening cover comprising a plurality of cover members installed along a circumferential direction of the inner circumferential surface of the furnace opening unit whereon a lower end of the reaction container is connected and wherethrough a substrate retainer is loaded and unloaded, each of the cover members comprising:
• a vertical side portion running along a corresponding part of the inner circumferential surfaced,
• a horizontal portion extending in a horizontal direction from an upper end of the side portion,
• two openings formed on the side portion at a same height and hooked to corresponding two of the projections disposed on the inner circumferential surface, and
• a protrusion protruding toward the inner circumferential surface and interposed between the two openings located left and right of the protrusion, respectively, on the side portion so as to contact with the inner circumferential surface without being fixed to the inner circumferential surface,
• wherein a gap is formed between the side portion and the inner circumferential surface of the furnace opening unit in a state where the two openings are hooked respectively to the two of the projections disposed on the inner circumferential surface and the protrusion is in contact with the inner circumferential surface.