Patent ID: 7211459

Claim:
A fabrication method of an ion sensitive field effect transistor (ISFET) comprising: providing a non-single-crystal silicon-base substrate; forming a polysilicon layer above the non-single-crystal silicon-base substrate; forming a source and a drain in the polysilicon layer, with a predetermined channel region formed between the source and the drain in the polysilicon layer; forming an insulating layer with a first contact hole and a second contact hole above the polysilicon layer, wherein the first contact hole and the second contact hole partially expose the source and the drain exposed, respectively; forming a first electrode and a second electrode, wherein the first electrode and the second electrode are electrically coupled with the source and the drain by the first contact hole and the second contact hole, respectively; forming a passivation layer with an opening above the insulating layer, wherein the passivation layer covers the first electrode and the second electrode, and the opening partially exposes the insulating layer above the predetermined channel region; and forming an ion sensitive gate in the opening above the insulating layer.