Plasma etching method

A plasma etching method comprising:

• a step of placing a processing subject substrate inside a processing vessel;
• a deposition step of supplying, into the processing vessel, a first processing gas that includes at least one gas including either or both of a fluorine atom and a carbon atom and a second processing gas, differing from the first processing gas, that has a noble gas as a main component and may include a gas including either or both of a fluorine atom and a carbon atom to provide an atmosphere containing the first processing gas and the second processing gas inside the processing vessel, and forming a thin film on at least one surface of the processing subject substrate;
• and
• an etching step of providing an atmosphere containing at least the second processing gas inside the processing vessel and plasma etching the processing subject substrate on which the thin film has been formed, wherein
• the deposition step and the etching step are switched between and implemented alternately, and
• when an atmosphere containing the first processing gas and the second processing gas is provided inside the processing vessel in the deposition step, the atmosphere is configured to contain at least 2.4 times and not more than 3.1 times more fluorine atoms than carbon atoms by mass.