| 摘要 |
PURPOSE:To reduce the processes of information writing by a method wherein the first threshold voltage is changed to the second one by irradiating a MISFET having the first threshold voltage with X-ray excellent in permeability. CONSTITUTION:After a mask 19 is formed, the entire surface is irradiated with X rays, and thus the threshold voltage of the MISFET other than at the part covered with the mask, i.e., MISFETQ12 is so controlled as to become a desired value e.g. approx. 0.5V. The threshold voltage of the n-channel MISFET is reduced by X ray irradiation. Thereby, in the channel-forming part 20 of the MISFETQ12, threshold voltages over 5V whereby this device does not turn on even when for example an operating voltage of approx. 5V is impressed on the gate electrode can be obtained. In the channel-forming part of the other MISFET, a threshold voltage e.g. of approx. 0.5V whereby this device turns ON when an operating voltage of approx. 0.5V is impressed on the gate electrode can be obtained. |
