PURPOSE: To improve processing precision and a speed for a sample, by applying high-frequency power to the second electrode independently of the first electrode and depositing a material, which is dispersed from the second electrode, on a sample and etching an etching protective film as well as forming it on the surface of the sample.

CONSTITUTION: A gas G1 having gaseous characteristics I and III is made to flow into a processing chamber 1. When high-frequency power is applied to the first electrode 3 under a condition of a point A, anisotropic etching on the first stage is performed and a pattern 17' of polycrystal Si is formed and a conventional etching remnant 17" is generated on a steep step-difference part 19. Then, while the gas G1 is exhausted, a gas G2 is supplied. When the high-frequency power is applied to the second electrode 13 under the condition of a characteristic point C shown in a figure, an etching protective film is deposited on a sample 2. Successively, when the high-frequency power is applied to the first electrode 3 so that an etch rate comes to a point B' shown in the figure, the etching protective film is removed on the other region excepting a side wall of the steep step-difference part. When the power application to the first electrode 3 is controlled thereafter so that the etch rate comes to a point B, the etching processing is promoted in the direction in which the sample 2 becomes thicker.