The present disclosure relates to a solid-state image capturing element capable of suppressing a dark current, a manufacturing method thereof, and an electronic device. Provided is a solid-state image capturing element including: a photoelectric conversion unit formed outside a semiconductor substrate; and a charge retention section that is formed in the semiconductor substrate and retains charges generated in the photoelectric conversion unit. Among surfaces of the charge retention section, a bottom surface on a side opposite to a surface of a gate side of a transistor formed in the semiconductor substrate is covered by an insulation film. The present disclosure can be applied to, for example, solid-state image capturing elements and the like.