A solid-state imaging device includes a photoelectric conversion unit that includes a first region of a first conductivity type and a second region of a second conductivity type between which a pn junction is formed, the first region and the second region being formed in a signal-readout surface of a semiconductor substrate, the second region being located at a position deeper than the first region; and a transfer transistor configured to transfer signal charges accumulated in the photoelectric conversion unit to a readout drain through a channel region that lies under a surface of the first region and horizontally adjacent to the photoelectric conversion unit, the transfer transistor being formed in the signal-readout surface. The transfer transistor includes a transfer gate electrode that extends from above the channel region with a gate insulating film therebetween to above the first region so as to extend across a step.