A carbon-loss-damage in a low-dielectric-constant film (porous SiOCH) for the silicon LSI devices was qualitatively investigated. It was found that the damage induced by plasma processes was dependent not only on the kinds of incident reactive species in plasmas, but also on the carbon bonding structure in the porous SiOCH film. Ion species in Ar and He plasmas and oxygen atoms induced sever damage on the film. Nitrogen and hydrogen atoms induced the damage relatively near the surface region of the film. Metastable-state atoms of Ar and He also induced the damage only the surface of the film. As a result of the comparison between methyl groups and methylene bridges in the film, the bonding state of methylene-bridge had larger resistance to the plasma damage than that of methyl group.