A storage device according to an aspect of the present disclosure includes a storage tank, a heating mechanism, and a controller. The storage tank stores a processing liquid that contains an aqueous solution of phosphoric acid and an additive. The heating mechanism heats the processing liquid that is stored in the storage tank. The controller controls the heating mechanism to execute a concentration maintaining process where a temperature of the processing liquid is adjusted in such a manner that an amount of evaporation of water for the processing liquid in the storage tank approaches an amount of absorption of moisture for the processing liquid in the storage tank.

The present invention provides an apparatus for treating a substrate. The apparatus of processing a substrate includes: a treatment bath having an receiving space accommodating treatment liquid, and treating a plurality of substrates; and a supporting unit supporting the substrates in the treatment bath, wherein the supporting unit includes: a support having a first supporting rod supporting end portions of the substrates in a vertical state; and a fixing plate coupled to the support and fixing the support, a plurality of first slots in which edges of the substrates are inserted is formed at the first supporting rod, each of the plurality of first slots is defined by a first side, a second side facing the first side, and a bottom, a front and a rear of the first slot are open toward the receiving space, and the bottom of the first slot comprises contact protrusions protruding upward from a lower end of the first side of the first slot and supporting lower end portions of the substrates.

A substrate processing method includes generating an etching liquid by adding a silicic acid compound to an alkaline processing liquid, and etching a polysilicon film formed on a substrate with the etching liquid.