| 摘要 |
PURPOSE:To enhance Ion/Ioff, to realize a high-speed response and to stabilize a potential at a substrate by a method wherein a polysilicon active layer is piled up on a low-resistance polysilicon layer formed on an insulating substrate, the low- resistance polysilicon layer is used as a diffused source and a prescribed channel region of the polysilicon active layer is lightly doped by thermal diffusion with a specific impurity. CONSTITUTION:A PSG film 11 and an OCD film 12 are formed on a polysilicon layer 2 formed on a quartz substrate 1; after the unnecessary part has been removed, a BSG film 13 is formed on the whole surface. Low-resistance polysilicon layers 2-a, 2-b are formed; each layer of PSG, OCD and BSG is removed; a polysilicon active layer 3 is formed. If the unnecessary region excluding a prescribed part is removed and a thermal oxide film 14 is formed, B or P is lightly introduced into the polysilicon active layer 3 from the low-resistance polysilicon layer. A polysilicon layer 15 to become a gate electrode 5 is formed; the gate electrode 5, a gate insulating film 4, a PSG film 21 and an OCD film 22 are formed; a BSG film 23 is formed on the whole surface. By means of solid-phase thermal diffusion, impurities of the PSG film 21 and the BSG film 23 are thermally diffused, and a source region and a drain region 3-a, 3-b are formed; after the PSG film 21, the OCD film 22 and the BSG film 23 have been removed, an interlayer insulating film 6 is formed. |
