In a field of manufacturing semiconductor devices, a plasma processing device has been used to perform a predetermined processing (e.g., etching or film formation) on a substrate to be processed (e.g., a semiconductor wafer) accommodated in a processing chamber by applying a plasma generated in the processing chamber thereto. 
In such a plasma processing device, a state of the plasma needs to be kept suitable for the plasma processing in order to perform a good processing.  For such reason, conventionally there are numerous plasma processing devices incorporating therein a magnetic field forming mechanism which forms a magnetic field for controlling the plasma. 
There are known a dipole type and a multi-pole type for such magnetic field forming mechanism.  The dipole type mechanism forms a dipole magnetic field in a predetermined direction above a horizontally disposed substrate to be processed such as a semiconductor wafer or the like having a to-be-processed surface facing upward.  The multi-pole type mechanism, which includes a plurality of N and S magnetic poles alternately disposed around a horizontally disposed substrate to be processed such as a semiconductor wafer or the like having a to-be-processed surface facing upward, forms a multi-pole magnetic field to surround the periphery of the semiconductor wafer, while avoiding formation of the multi-pole magnetic field thereabove. 
As described above, there have been plasma processing devices known to form a predetermined multi-pole magnetic field around the periphery of a substrate to be processed such as a semiconductor wafer in a processing chamber; to control a state of a plasma by the multi-pole magnetic field; and to carry out a plasma process such as etching or the like. 
According to the findings of the inventors of the present invention, it is shown that there are two kinds of processes in a plasma process (e.g., a plasma etching) as described below. 
A first kind of process in which the plasma etching process is performed while the multi-pole magnetic field is formed as mentioned above, improves an in-surface uniformity of the etching rate.  Contrary to the first kind of process, a second kind of process which also improves the in-surface uniformity of the etching rate performs plasma etching process in the absence of the multi-pole magnetic field. 
For instance, in an etching process of a silicon oxide film or the like, the in-surface uniformity of the etching rate (etching velocity) can be improved when etched in the presence of the multi-pole magnetic field in comparison with a case of performing etching in the absence of the multi-pole magnetic field.  In case of performing etching in this process without the multi-pole magnetic field, there is a non-uniformity of the etching rate, i.e., the etching rate is increased in a center region of the semiconductor wafer and decreased in a periphery portion thereof. 
On the other hand, in an etching process of an organic-based low dielectric film (so-called Low-K) or the like, the in-surface uniformity of the etching rate can be improved when etched in the absence of the multi-pole magnetic field in comparison with a case of performing etching in the presence of the multi-pole magnetic field.  In particular, when etched in the presence of the multi-pole magnetic field in such a process, the etching rate is decreased in a center region of the semiconductor wafer and increased in a periphery portion thereof. 
Employing electromagnets in the aforementioned magnetic field forming mechanism facilitates formation and removal of the magnetic field.  However, doing so increases power consumption and for such reason, permanent magnets are employed instead of the electromagnets in most devices. 
However, in case of employing the permanent magnets, additional steps of attaching and detaching the magnetic field forming mechanism are required for formation and removal of the magnet field, which hinders facilitation of such processes.