PURPOSE: To easily remove a residual resist on a semiconductor substrate by exerting an ultrasonic vibration energy by using an ultrasonic pure-water cleaning apparatus.

CONSTITUTION: A semiconductor substrate 1 is coated with a photoresist 2; then, the photoresist 2 is removed by using sulfuric acid, nitric acid or the like. After that, an ultrasonic vibration energy is exerted by using an ultrasonic pure-water cleaning apparatus; a residual resist is decomposed. Thereby, the residual resist can be removed completely; a clean semiconductor device can be obtained. In addition to the ultrasonic oscillation energy by using the ultrasonic pure-water cleaning apparatus, a similar effect can be obtained by using an ultrasonic organic-solvent cleaning apparatus or an ultrasonic sulfuric-acid cleaning apparatus.