Sacrificial film forming method, substrate treatment method, and substrate treatment device

In a method of forming a sacrificial film, a liquid film 26 of a sacrificial polymer solution 25 which covers the front surface of a substrate W in which patterns P are formed is heated from the side of the substrate, the solution in contact with the front surface of the substrate is evaporated and thus the liquid film is dried in a state where the liquid film is held on at least tip end portions other than base portions of the patterns, with the result that a sacrificial film is formed. In a substrate processing method and a substrate processing apparatus, the front surface of the substrate is processed while the collapse of the patterns is suppressed or prevented by utilization of the formed sacrificial film.