Plasma nitriding

Patent Granted Disclosed is a plasma nitriding method wherein a nitriding is performed at a process temperature of not less than 500 DEG C in a process chamber of a plasma processing apparatus by causing a microwave-excited high-density plasma of a nitrogen-containing gas, which is formed by introducing a microwave into the process chamber using a multi-slotted planar antenna, to act on silicon in the surface of an object to be processed.