Patent ID: 8216378

Claim:
A reaction tube for a semiconductor process, the reaction tube having an inner space for performing a heat process on a plurality of target objects stacked at intervals under a vacuum state, the reaction tube being integrally made of an electrically insulating and heat-resistant material and comprising: a cylindrical sidewall that has a load port at a lower end for loading and unloading the target objects to and from the reaction tube, the sidewall defining a cylindrical side profile of the inner space; and a circular ceiling wall that closes an upper end of the sidewall and has a flat inner surface extending in a direction perpendicular to an axial direction of the sidewall, the flat inner surface of the ceiling wall defining a flat upper profile of the inner space, wherein the ceiling wall is integrated with the sidewall through an annular outer end of the circular ceiling wall present directly above the sidewall and includes an annular groove formed in a peripheral region of an outer surface opposite to the flat inner surface along the annular outer end, such that the annular groove has an annular outer side surface inclined outward and upward from a bottom thereof to the annular outer end and the ceiling wall has a larger wall thickness at the annular outer end than at the bottom of the annular groove, to relax a stress caused on the annular outer end due to the vacuum state in the inner space.