| 摘要 |
PURPOSE:To improve the characteristic of a MOS thin film transistor (TFT) by enlarging the grain size of the polysilicon film of the bulk section (source- drain channel area section) of the TFT and, at the same time, to make the polysilicon film compact in texture. CONSTITUTION:The polysilicon film of the bulk section of a MOS thin film transistor (TFT) is formed by continuously forming a polysilicon film 3 containing a TV group metal and another polysilicon film 3 containing no impurity. The grain size of the first-layer polysilicon of the channel section of the TFT is adjusted by adjusting the introducing amount of the impurity at the time of forming the first-layer polysilicon. Therefore, the TFT can have a low turning-off current, high turning-on current, and high ON/OFF ratio. In addition, since the impurity is introduced into the polysilicon film of the channel section without performing any ion implanting process and the introducing quantity of the impurity is adjusted at the time of forming the polysilicon, the threshold voltage Vth of the TFT can be controlled. |
