PURPOSE: To shorten a cleaning time by supplying SF6 or a mixture gas containing SF6 as cleaning gas, and generating a plasma in the cleaning gas.

CONSTITUTION: SiCl4 is introduced from an etching gas source 2 into a treating chamber 1, a high frequency power is applied by a high frequency power source 5 to a lower electrode 4 to generate a plasma in etching gas. Then, in order to remove reactive products adhered and deposited in the chamber 1, cleaning gas is introduced from a cleaning gas source 6 into the chamber 1, a high frequency power is applied to the electrode 4 similarly to the time of etching to generate a plasma in the cleaning gas. In this case, SF4 and CF4 are employed. This is because the plasma is generated in the SF6 to generate a large quantity of volatile silicon fluoride generated by the reaction of Si with the radical and ions and removed by vacuum evacuation. Accordingly, the cleaning time in the chamber 1 is considered to be shortened.