The present technology relates to a solid-state imaging device, a manufacturing method of a solid-state imaging device, and an electronic device, in which degradation of transfer characteristics of a photo diode can be suppressed. A floating diffusion is formed to reach the same depth as a layer of a photo diode formed on a silicon substrate, and a transfer transistor gate is formed therebetween. A channel that is opened/closed by control of the transfer transistor gate is formed in the silicon substrate formed with the photo diode. With this configuration, charge accumulated in the photo diode can be transferred to the floating diffusion in a vertical direction relative to the depth direction, and degradation of transfer characteristics caused by elimination of the transfer channel can be suppressed by setting the transfer channel in the depth direction. The present technology can be applied to a solid-state imaging device.