The invention is regarding to solid-state imaging device. A solid-state imaging device consistent with the present invention includes, a plurality of unit cells on a semiconductor substrate of a first conductivity type, each unit cell including a photoelectric conversion unit comprising a photodiode having a diffusion layer of a second conductivity type and a signal scanning circuit unit; a trench isolation region for isolating the photoelectric conversion unit from the signal scanning circuit unit, the trench isolation region being formed in the semiconductor substrate;a first element-isolating diffusion layer of the first conductivity type formed under a bottom face of the trench isolation region down to a position deeper than the diffusion layer of the photodiode from the surface of the semiconductor substrate.