PURPOSE: To make the etching speed of a wafer uniform, by providing temperature regulating pipes on the outer surface of a reaction container wherein a semiconductor wafer is treated with plasma, circulating liquid having a preset temperature, and keeping the temperature of the container at a specified temperature.

CONSTITUTION: A semiconductor wafer 11 is mounted on a wafer table 10 that is provided in a reaction chamber 2 in a reaction container 1. The pressure in the reaction chamber 2 is kept at a specified pressure of process gas. A high frequency power source is applied to an upper electrode plate 13 and the table 10 that becomes a lower electrode part plate. Thus, plasma is yielded. Temperature regulating pipes 14 are provided on the outer surface of the container 1. Liquid 17 which is kept at a preset temperature with a temperature regulator 16 is circulated through the pipes 14. Thus, the container 1 is kept at a specified temperature. Therefore, the convection of the gas in the reaction chamber 2 is made uniform. In this way, the etching speed of the wafer 11 is made uniform, and the attachment of products during etching on the inner wall of the container is prevented.