To provide a rapid heat treatment reactor for processing improved semiconductor substrate.

The rapid heat treatment reactor has a rapid heat treatment reaction chamber vessel, a table which is arranged around the rapid heat treatment reaction chamber vessel and comprises a top surface, a shell arranged at a first position so as to contact with the top surface of the table, a rail which is fastened on the table, while extending in a first direction perpendicular to the top surface of the table, and a connection part which is movably connected to the rail so that the shell can be moved to a second position apart from the top surface of the table along the rail, when needed and comprises a plurality of connectors selectively detachable from the shell. When the shell is present at the second position, by detaching one of the plurality of connectors from the shell means, the shell can be made to turn with the left connectors as the axes.