A method of fabricating a semiconductor structure includes disposing a metal catalyst on a surface of a semiconductor. Thereafter, metal assisted chemical etching is performed, including holding the semiconductor immersed in an etchant solution and catalyzing an etching chemical reaction between the etchant solution and the semiconductor using the metal catalyst to etch the semiconductor to form a channel in the semiconductor. During at least a portion of the metal assisted chemical etching the semiconductor is held immersed in the etchant solution with a surface normal of the surface of the semiconductor at a non-zero angle respective to gravity. In some examples, an orientation of the semiconductor is changed during the metal assisted chemical etching to form the channel in the semiconductor with at least one bend or curved portion.

Provided is an imaging element including a photoelectric conversion unit formed by stacking a first electrode, a photoelectric conversion layer and a second electrode. The photoelectric conversion unit further includes a charge storage electrode which is disposed to be spaced apart from the first electrode and disposed opposite to the photoelectric conversion layer via an insulating layer. The photoelectric conversion unit is formed of N number of photoelectric conversion unit segments, and the same applies to the photoelectric conversion layer, the insulating layer and the charge storage electrode. An n.sup.th photoelectric conversion unit segment is formed of an n.sup.th charge storage electrode segment, an n.sup.th insulating layer segment and an n.sup.th photoelectric conversion layer segment. As n increases, the n.sup.th photoelectric conversion unit segment is located farther from the first electrode. A thickness of the insulating layer segment gradually changes from a first to N.sup.th photoelectric conversion unit segment.

Provided is an imaging element including a photoelectric conversion unit formed by stacking a first electrode, a photoelectric conversion layer and a second electrode. The photoelectric conversion unit further includes a charge storage electrode which is disposed to be spaced apart from the first electrode and disposed opposite to the photoelectric conversion layer via an insulating layer. The photoelectric conversion unit is formed of N number of photoelectric conversion unit segments, and the same applies to the photoelectric conversion layer, the insulating layer and the charge storage electrode. An n.sup.th photoelectric conversion unit segment is formed of an n.sup.th charge storage electrode segment, an n.sup.th insulating layer segment and an n.sup.th photoelectric conversion layer segment. As n increases, the n.sup.th photoelectric conversion unit segment is located farther from the first electrode. A thickness of the insulating layer segment gradually changes from a first to N.sup.th photoelectric conversion unit segment.