Substrate processing liquid, substrate processing method and substrate processing apparatus

The present invention provides a substrate processing liquid which is suitable for a substrate having a layer to be etched, wherein at least one of the bottom wall and the side wall of a trench structure is configured from a metal or a compound of the metal. This substrate processing liquid comprises a chemical agent that contains H2O2 molecules or HO2-, each of which serves as an etchant that etches the metal, and a first complex forming agent that contains anions that form a complex together with ions of the metal; and this substrate processing liquid is adjusted to have a pH of 1 to 6. Consequently, this substrate processing liquid enables etching of a substrate at an excellent etching rate.