Method of forming a novel self-aligned offset thin film transistor and the structure of the same

Abstract

The method includes patterning a first polysilicon layer on a substrate. A first dielectric having a first via hole is defined over the substrate. A second polysilicon layer is formed along the surface of the first dielectric layer and refilled into the first via hole. Then, an etching is used to etch the layer. A residual portion of the layer is located at the lower portion of the first via hole. An undoped polysilicon is then patterned on the first dielectric layer and along the surface of the first via hole. An isolation structure is then refilled into the first via hole. An oxide layer is formed on the first polysilicon, the first dielectric layer and the upper surface of isolation structure to act as the gate oxide of the TFT. Then, the oxide and the first dielectric layer are etched to define a second via hole. A further polysilicon layer is pattern on the first dielectric layer and refilled into the second via hole for defining the gate. Then, an ion implantation is employed to dope conductive species into the undoped polysilicon layer uncovered by the gate structure, thereby forming the doped region to act as source or drain. An isolation layer is deposited and a third via hole is generated in the isolation layer. A further polysilicon is then patterned on the second dielectric layer.