| 摘要 |
PURPOSE:To increase the threshold voltage of a N channel transistor besides its breakdown voltage, by setting the depth of a P-type impurity region between 10 and 20mum when forming a C-IGFET and by fixing the threshold voltage to a fixed value through P-type impurity ion injection. CONSTITUTION:Onto N-type Si substrate 31, oxidized film 32 is adhered, an aperture is made in the P-well formation region, and P-type impurity ion 33 is injected to form P-type region 34. Through forced diffusion, region 34 is expanded to obtain P -well region 39 of fixed depth 10 to 20mum, where N-type source and drain regions 37 and 38 of the N-channel element are formed by diffusion. In substrate 31, the P-type source and drain regions 43 and 44 of the P-channel elements are formed away from region 39 by diffusion, and P-type impurity ion 48 is injected in order to fix the threshold voltage of the P-channel element. Further, P-type impurity ion 49 is also injected in order to increase the threshold voltage of the N-channel element. |
