| 摘要 |
PURPOSE:To provide a bottom-gate type thin-film transistor of uniform quality by making its channel region thin and source/drain regions thick. CONSTITUTION:A polysilicon layer 103 is deposited on a semiconductor substrate 101 covered completely with a silicon oxide film 102. After the polysilicon layer is doped with an impurity, silicon nitride 104 is deposited on the polysilicon layer. The nitride is patterned, and it is used as a mask to etch the polysilicon so that an undercut may be formed. Another polysilicon layer 105 is formed thinner than the polysilicon layer 103, and an impurity is introduced. A silicon oxide layer 106 is formed on the polysilicon layer, and then the silicon nitride 104 and the polysilicon layer 105 are removed, before a polysilicon layer 107 is formed over the whole structure. Then, source and drain regions are formed by laser annealing. |
