Method of manufacturing thin film transistor

Claim 1

A method for making a thin film semiconductor device comprising the steps of: providing a transparent substrate having an upper surface and an opposed lower surface; forming a gate electrode on the upper surface having a width dimension; forming an impurity shielding layer on the upper surface and exposed upper surface of the gate electrode; forming a gate insulating film on the impurity shielding layer; applying a photoresist layer on said gate insulating film; exposing the substrate from the lower surface side to light to develop exposed portions of the photoresist layer; removing exposed portions of the resist layer to provide a remaining unexposed resist portion above the gate electrode, said resist portion having a first width substantially equal to the width of the gate electrode; heating and flowing the resist portion to provide a deformed resist portion having a second width greater than said first width; forming a relatively higher concentration impurity containing first amorphous silicon layer on said deformed resist portion and adjacent portions of said gate insulating film; removing the deformed resist portion and any overlying portions of the first impurity containing amorphous silicon layer to provide first and second separated portions of the impurity containing first amorphous silicon layer on opposed sides of the gate electrode and spaced from the gate electrode by an offset width; forming a relatively lower concentration impurity containing second amorphous silicon layer on said first and second portions and exposed portions of said gate insulating film; laser annealing to diffuse and activate impurities in said first and second amorphous silicon layers to define source and drain regions on opposite sides of the gate electrode and spaced from the gate electrode by an offset width; and thereafter, forming source and drain electrodes disposed in ohmic contact with said source and drain regions, respectively.

Claim 2

A method for making a thin film semiconductor device comprising the steps of: providing a transparent substrate having an upper surface and an opposed lower surface; forming a gate electrode on the upper surface having a width dimension; forming an impurity shielding layer on the upper surface and exposed upper surface of the gate electrode; forming a gate insulating film on the impurity shielding layer; applying a photoresist layer on said gate insulating film; exposing the substrate from the lower surface side to light to develop exposed portions of the photoresist layer; removing exposed portions of the resist layer to provide a remaining unexposed resist portion above the gate electrode, said resist portion having a first width substantially equal to the width of the gate electrode; heating and flowing the resist portion to provide a deformed resist portion having a second width greater than said first width; forming a relatively higher concentration impurity containing first amorphous silicon layer on said deformed resist portion and adjacent portions of said gate insulating film; removing the deformed resist portion and any overlying portions of the first impurity containing amorphous silicon layer to provide first and second separated portions of the impurity containing first amorphous silicon layer on opposed sides of the gate electrode and spaced from the gate electrode by an offset width; forming a relatively lower concentration impurity containing second amorphous silicon layer on said first and second portions and exposed portions of said gate insulating film; laser annealing to diffuse and activate impurities in said first and second amorphous silicon layers to define source and drain regions on opposite sides of the gate electrode and spaced from the gate electrode by an offset width; and thereafter, forming source and drain electrodes disposed in ohmic contact with said source and drain regions, respectively.