Plasma processing method

The present invention provides a technology which is capable of processing a ruthenium pattern so that the ruthenium pattern has a desired cross-sectional shape by performing a step for forming and removing a side wall protection film by a simple process, while suppressing pattern surface contamination with impurities, and suppressing the formation of bowing or the like. The present invention provides a plasma processing method for etching a ruthenium film by means of a plasma, the plasma processing method comprising: a first step in which the ruthenium film is etched by means of a plasma that is generated using a mixed gas of an oxygen gas and a halogen gas; a second step in which a ruthenium compound is formed on the side wall of the etched ruthenium film, after the first step, by means of radicals that are generated by a plasma which is generated using a halogen gas; a third step in which the ruthenium film is etched, after the second step, by means of a plasma that is generated using a mixed gas of an oxy