Difference of chemical reactivity of source gases towards photo and plasma excitations was utilized to produce amorphous superlattices continuously. Molecular nitrogen was scarcely decomposed by Hg sensitized photochemical reaction of r.f. plasma but was by microwave plasma. Thus, pulsed microwave plasma and photo CVD produced a-Si:H/a-SiN:H superlattices from a mixture of Si 2H 6 and N 2. A quantum size effect in the superlattices was verified from the increase of optical band gap with the decrease of well layer thickness. Some of the superlattices fabricated have photo conductivities higher than the a-Si:H films prepared by the photo CVD. A specific band profile of the superlattice was evaluated by X-ray photoelectron and UV-VIS spectroscopies.