Apparatus and method for treating substrate

An apparatus for treating a substrate, the apparatus comprising:

• a process chamber having a process space therein;
• a support plate configured to support the substrate in the process space;
• a heater configured to heat the substrate supported on the support plate;
• an exhaust unit configured to evacuate the process space,
• wherein the exhaust unit includes:
• an exhaust duct;
• and
• a heat retainer having a retention space configured to retain heat released from the process space,
• wherein the retention space surrounds an adjacent area located adjacent to the process chamber in the exhaust duct,
• wherein the exhaust duct has a portion parallel with respect to an upper side of the process chamber,
• wherein the portion is contacted with the upper side of the process chamber,
• wherein the heat retainer includes a housing having the retention space therein,
• wherein the heat retainer further includes a shape retainer configured to maintain a shape of an upper wall of the housing,
• wherein the shape retainer includes a reinforcing plate coupled to a bottom surface of the upper wall to form an interior space enclosed by the upper wall and the shape retainer,
• wherein the interior space is filled with a gas, and
• wherein the interior space is provided in a state in which a flow of the gas to an outside of the interior space is completely blocked.