PURPOSE: To sufficiently improve the withstanding voltage characteristic of a substrate after cleaning by adding phosphoric acid ions to cleanser which mainly contains mixture solution of ammonia water and hydrogen peroxide water.

CONSTITUTION: Phosphoric acid ions are contained in a range of 5ppb to 500ppb to cleanser which mainly contains mixture solution of ammonia water and hydrogen peroxide water. The phosphoric acid ions may be replaced by phosphoric acid, phosphoric acid 1 ammonium, phosphoric acid 2 ammonium or phosphoric acid 3 ammonium, but phosphate which contains cation except hydrogen ions and ammonium ions is unpreferable to deteriorate the characteristic of an element. The step of adding the phosphoric acid ions is preferably added in advance after refining the hydrogen peroxide water. That is, after impurities are sufficiently removed from the hydrogen peroxide water, the phosphoric acid ions are newly added to the refined hydrogen peroxide water for mixing.