A solid state imaging device includes: an imaging region formed in an upper part of a substrate made of silicon to have a photoelectric conversion portion, a charge accumulation region of the photoelectric conversion portion being of a first conductivity type; a device isolation region formed in at least a part of the substrate to surround the photoelectric conversion portion; and a MOS transistor formed on a part of the imaging region electrically isolated from the photoelectric conversion region by the device isolation region. The width of the device isolation region is smaller in its lower part than in its upper part, and the solid state imaging device further includes a dark current suppression region surrounding the device isolation region and being of a second conductivity type opposite to the first conductivity type.