lamps 6 7 by e px 39 and the threshold value of the activation energy for dissociating the disilane molecule by e th they have the following values here when each one photon is absorbed from the light source 5 and the light source 6 or 7 since the light from xe lamp is continous light excitation may be possible to any energy level at the region within this is schematically shown in fig2 and in this case resonance absorption can occur to the respective energy levels such as e 1 e th e 2 e 3 e 4 etc whereby the deposition speed can be improved by light absorption with good efficiency it is preferable for more efficient light absorption and prevention of one photon absorption by laser that e p should satisfy the condition of e p lt e th as in this examples also as for e px although the influence of this on one photon absorption may be little it should desirably satisfy the condition of e px lt e th also in the device shown in fig1 two ellipsoidal mirror built in type xe lamps 6 7 have been employed for the effects of enhancing the intensity of incident light and enhancing the deposition speed these effects are backed up by the knowledge that 34 the transition probability.