Transistor, electronic device, manufacturing method of transistor

A transistor comprising:

• a first conductive layer over a substrate, the first conductive layer functioning as a floating gate;
• a first insulating layer and a second insulating layer over the first conductive layer;
• a semiconductor layer over the first insulating layer;
• a third insulating layer over the semiconductor layer and the first conductive layer;
• a second conductive layer over the second insulating layer, the second conductive layer functioning as a control gate;
• and
• a third conductive layer over the third insulating layer, the third conductive layer functioning as a gate electrode,
• wherein the first conductive layer comprises:
• a first region overlapping with the semiconductor layer with the first insulating layer therebetween;
• a second region overlapping with the second conductive layer with the second insulating layer therebetween in a channel width direction;
• and
• a third region overlapping with the third conductive layer with the third insulating layer therebetween,
• wherein a thickness of the first insulating layer is larger than a thickness of the second insulating layer,
• wherein the second conductive layer does not overlap with the semiconductor layer and the third conductive layer in a top view, and
• wherein the first conductive layer is configured to be injected with a charge by applying a voltage between the second conductive layer and the third conductive layer.