Abstract: A substrate processing apparatus includes a reaction tube, the reaction tub including an inner tube made of quartz and an outer tube made of quartz; a manifold made of quartz disposed under the outer tube, a top surface of the manifold being in air-tight contact with a bottom surface of the outer tube via a sealing member; a seal cap cover made of quartz disposed under the manifold, a top surface of the seal cap cover being in air-tight contact with a bottom surface of the manifold via a sealing member; a seal cap covered by the seal cap cover, a top surface of the seal cap being in air-tight contact with a bottom surface of the seal cap cover via a sealing member; and at least one protrusion disposed at the bottom surface of one of the outer tube, the manifold, the seal cap cover, and combinations thereof.

Abstract: When a quartz part is placed on a floor, the inside of a furnace is not polluted by contaminants attached from the floor to a seal surface of the quartz part and entering the inside of the furnace. A substrate processing apparatus includes a reaction tube, a first joining surface, a second joining surface, and a third joining surface. The reaction tube includes a quartz inner tube and a quartz outer tube. The first joining surface is configured to air-tightly join the outer tube and a quartz manifold. The second joining surface is configured to air-tightly join the manifold and a quartz seal cover. The third joining surface is configured to air-tightly join the seal cover and a seal cap. An O-ring is installed at least one of the first, second, and third joining surfaces, and a protrusion is installed outside the O-ring installed at the jointing surface.