Nanometer silicon crystallites were fabricated by annealing a-Si:H/a-SiNx:H multiquantum well (MQW) structures with an excimer laser. The films were prepared by rf plasma enhanced chemical vapor deposition. Visible electroluminescence (EL) has been observed at room temperature from the crystallized samples that had Si well layers narrower than 4.0 nm. The EL spectra showed multiple peaks at wavelengths around 600 and 700 nm, and an orange-red colored light emission could be observed by the naked eye. The onset voltage of visible light emission was 7 V. The EL intensity increased dramatically with an increasing laser irradiation value, and the EL peak shifted towards shorter wavelengths with a decrease in the Si well layer thickness. Tn agreement with the theoretical model, the visible EL phenomenon can be interpreted as the result of carrier injection into the nanosized Si crystallites in the MQWs, and radiation recombination via silicon quantum well states.