Polydiode structure for photo diode

1. An integrated circuit device for converting an incident optical signal into an electrical signal, comprising:

a semiconductor substrate;

a well region formed inside the semiconductor substrate;

a dielectric layer formed over the well region; and

a layer of polysilicon for receiving the incident optical signal, formed over the dielectric layer, including a p-type portion, an n-type portion and an intrinsic portion disposed between the p-type and n-type portions,

wherein the well region is biased to control the layer of polysilicon for providing the electrical signal.

2. The device of claim 1 , further comprising a first isolation structure and a second isolation structure spaced apart from the first isolation structure.

3. The device of claim 2 , wherein at least one of the first or second isolation structure overlaps the well region.

4. The device of claim 2 , wherein the intrinsic region overlaps a portion of the well region between the first and second isolation structures.

5. The device of claim 1 , further comprising a diffused region formed inside the well region.

6. The device of claim 5 , wherein the diffused region is biased to cause the well region to be biased to control the layer of polysilicon for providing the electrical signal.

7. The device of claim 5 , further comprising a diffused region formed outside the well region.

8. The device of claim 1 , wherein the intrinsic portion is contiguous with the p-type and n-type portions.