Patent ID: 7208811

Claim:
A photo-detecting device for converting incident light into electric charges comprising: a first silicon substrate having a pn-junction; a first SOI substrate in which a second silicon substrate having a pn-junction is formed on a first SOI insulation layer; and a second SOI substrate in which a third silicon substrate having a pn-junction is formed on a second SOI insulation layer; a light-collecting film that is formed on the surface of said second SOI substrate irradiated with the light, and that is made of a photonic crystal; and a photocatalyst film that is formed on a surface of the photonic crystal irradiated with the light, and that is made of titanium oxide, wherein said first silicon substrate, said first SOI substrate and said second SOI substrate are sequentially stacked, said each pn-junction of said first silicon substrate, said second silicon substrate and said third silicon substrate forms a photodiode that converts the light into electric charges, and a depth of said pn-junction of said each silicon substrate corresponds to an absorption depth of the light to be converted into electric charges, the depth of said pn-junction being a depth from a surface of said second SOI substrate irradiated with the light, and the titanium oxide has a photocatalyst function that is caused by visible light.