| 摘要 |
PURPOSE:To enable the restraining of an internal electric field which is enhanced according to miniaturization of a MOS transistor by introducing an impurity element of a small diffusion coefficient at one process of impurity doping in order to reduce the concentration gradually toward a channel of a drain. CONSTITUTION:An impurity of a small diffusion coefficient, e.g. As is used in case of NMOS. When the diffusion layers 32, 33 and 14 having inverse conductive types to that of a substrate 34 are subjected to one ion implantation through a film 31 and an oxide film 15, the concentration reduced gradually toward a channel because the film 31 has a thickness inclination and the diffusion layer 33 has a concentration gradient in a longitudinal direction of the channel of a MOS transistor. Accordingly, the strength of an electric field of a depletion layer region can be reduced without causing the reduction of an effective channel length. |
