The possibility for room temperature annealing of defects in MOS capacitors, induced from a MERIE-like reactor, has been investigated. It is established that, as time proceeds, plasma induced interface states density only decreases (3-5 times), but interface states are not completely annealed. The reduction depends only on the starting post-plasma treatment level of interface states. If the plasma conditions lead to an interface state level of similar to 10(12)-10(13) cm(-2) eV(-1), a reduction occurs. The results demonstrate that the effects responsible for room temperature reduction of the plasma defects take place very close to the Si-SiO2 interface. (The fixed oxide charge is stable and it does not change at all.) The process seems to be controlled by moisture transport to the Si-SiO2 interface.