with the refractive index difference from the n type silicon substrate taken into account and a thickness of about 500 to 1 000 u00e5 for the purpose of preventing light from being reflected by the surface of n type silicon substrate so that light may be effectively taken into the n type silicon substrate the sin also functions as a passivation film having a passivation effect to the p type diffusion layer during formation the passivation effect combined with the antireflection effect improves electrical properties of a solar cell although the antireflection passivation film of sin is described herein as a typical example it may be any of mgf 2 sio 2 al 2 o 3 sio sin tio 2 ta 2 o 5 and zns or even a stack of such layers as alluded to previously subsequently an antireflection passivation film 11 is formed on the back surface of n type silicon substrate the antireflection passivation film 11 is typically made of sin and formed by plasma enhanced cvd for example a gas mixture of sih 4 and nh 3 is diluted with n 2 and a gas plasma is created by glow discharge decomposition from which sin is deposited the antireflection passivation film is formed so as to have a refractive index of about 1 7 to 2 4 and a thickness of about 500 to 3 000 u00e5 with the passivation effect on n type diffusion layer mainly taken into account the film mainly functions as a passivation film having a passivation effect to the n type diffusion layer the passivation effect combined with the antireflection effect improves electrical properties.