Substrate processing method

A substrate processing method comprising:

• a phosphoric acid processing step that includes a step of supplying a phosphoric acid aqueous solution, which contains silicon, to a front surface of a substrate and processes the front surface of the substrate while forming a liquid film of the phosphoric acid aqueous solution having a silicon concentration lower than a saturation concentration of silicon;
• a liquid volume reducing step of reducing a volume of the phosphoric acid aqueous solution on the substrate, after the phosphoric acid processing step;
• a rinse step of supplying the front surface of the substrate with a rinse liquid having a temperature lower than that of the liquid film of the phosphoric acid aqueous solution supplied to the front surface of the substrate in the phosphoric acid processing step, and replacing the phosphoric acid aqueous solution on the front surface of the substrate with the rinse liquid, after the liquid volume reducing step;
• a first concentration maintaining step of maintaining a concentration of silicon contained in the liquid film of the phosphoric acid aqueous solution on the substrate at a concentration lower than the saturation concentration, until the liquid volume reducing step ends;
• and
• a second concentration maintaining step of maintaining a concentration of silicon contained in a liquid on the substrate at a concentration lower than the saturation concentration, until supplying of the rinse liquid ends in the rinse step.