Photodetection device and electronic device

A photodetection device comprising:

• a semiconductor layer having a first surface and a second surface located on opposite sides of the semiconductor layer in a thickness direction;
• and
• a plurality of pixels provided in the semiconductor layer, wherein
• each of the plurality of pixels includes:
• a photoelectric conversion part provided in the semiconductor layer;
• and
• two transfer systems that transfer signal electric charges generated by photoelectric conversion in the photoelectric conversion part to a corresponding second electric charge retaining part,
• each of the two transfer systems includes:
• a first electric charge retaining part and the second electric charge retaining part provided adjacent to the first surface of the semiconductor layer;
• a first transfer transistor that transfers the signal electric charges generated by photoelectric conversion in the photoelectric conversion part to the first electric charge retaining part;
• and
• a second transfer transistor that transfers the signal electric charges transferred by the first transfer transistor and retained in the first electric charge retaining part to the second electric charge retaining part,
• the first electric charge retaining part includes:
• a semiconductor region provided adjacent to the first surface of the semiconductor layer;
• and
• an electrode placed on the semiconductor region with an insulation film interposed between the electrode and the semiconductor region, and
• an upstream side of the electrode in a direction in which the signal electric charges are transferred is narrower than the downstream side of the electrode in the direction in which the signal electric charges are transferred.

An electronic device comprising:

• a photodetection device;
• an optical lens that forms an image of image light from a subject on an imaging surface of the photodetection device;
• and
• a signal processing circuit that performs signal processing on a signal output from the photodetection device, wherein
• the photodetection device includes:
• a semiconductor layer having a first surface and a second surface located on opposite sides of the semiconductor layer in a thickness direction;
• a photoelectric conversion part provided in the semiconductor layer;
• first and second electric charge retaining parts provided adjacent to the first surface of the semiconductor layer;
• a first transfer transistor that transfers signal electric charges generated by photoelectric conversion in the photoelectric conversion part to the first electric charge retaining part;
• and
• a second transfer transistor that transfers the signal electric charges transferred by the first transfer transistor and retained in the first electric charge retaining part to the second electric charge retaining part,
• the first electric charge retaining part includes:
• a semiconductor region provided adjacent to the first surface of the semiconductor layer;
• and
• an electrode placed on the semiconductor region with an insulation film interposed between the electrode and the semiconductor region, and
• an upstream side of the electrode in a direction in which the signal electric charges are transferred is narrower than a downstream side of the electrode in the direction in which the signal electric charges are transferred.