Disclosed is an apparatus for treating a substrate, the apparatus including: a vessel having a treatment space therein; a support unit for supporting a substrate in the treatment space; a supply port provided in the vessel, and for supplying a process fluid to the treatment space; and a filler unit disposed below the substrate supported on the support unit in the treatment space, in which the filler unit includes: a plate disposed opposite the substrate supported on the support unit; and a plurality of legs extending downwardly from a lower surface of the plate to support the plate within the vessel, a bottom wall of the vessel is formed with a groove defined by an inner surface and a bottom surface, the plate is positioned higher than the groove, and each of the plurality of legs is provided to be in contact with the inner surface forming the groove.

A substrate processing apparatus includes a first drying unit configured to perform a first drying process using a drying fluid on a substrate having a liquid film formed thereon, a first fluid supply unit configured to supply the drying fluid into the first drying unit, a second drying unit configured to perform a second drying process using the drying fluid on the substrate on which the first drying process is performed, a second fluid supply unit configured to supply the drying fluid into the second drying unit, a first door configured to control opening and closing of the first drying unit, and a second door configured to control opening and closing of the second drying unit, wherein the first door is opened when pressure in the first drying unit reaches a first transfer pressure, and the second door is opened when pressure in the second drying unit reaches a second transfer pressure.