Transistor and image sensor having the same

An image sensor comprising:

• a light receiving section configured to generate photocharges in response to incident light;
• and
• a driving section including a source follower transistor configured to generate an output voltage corresponding to a reference voltage of the image sensor in response to the photocharges,
• wherein the source follower transistor comprises:
• a substrate;
• a stack structure formed over the substrate by sequentially stacking a first conductive layer, an insulating layer and a second conductive layer, wherein the insulating layer is interposed between the first conductive layer and the second conductive layer;
• an open portion formed through the second conductive layer and the insulating layer so as to expose the first conductive layer;
• a channel layer formed along a surface of the open portion so as to be connected to the first conductive layer and extending onto the second conductive layer so as to be connected to the second conductive layer;
• and
• a gate is connected to the light receiving section and which is formed over the channel layer so as to overlap the second conductive layer.