PURPOSE: To lower threshold voltage by eliminating drawback of prior art, i.e., side effect of performance deterioration of MOSFET due to increase of threshold voltage.
CONSTITUTION: Impurities doped into the gate electrodes 7, 8 of a gate insulation film 6 are diffused through the gate insulation film 6 into a substrate 1 thus providing a shallow diffused layer at the channel part beneath the gate insulation film 6. Threshold voltage (Vth) is determined by the impurity concentration at the shallow channel part in a well of a MOS field effect transistor(MOSFET). Lowering of Vth is determined by the impurity concentration in a well at a depth close to the junction between source and drain. Consequently, Vth can be lowered without sacrifice of Vth-Lowering through shallow diffusion, at the channel part, of impurities of reverse type to those at the well in the gate electrodes 7, 8.
MITANI SHINICHIRO
OTSUKA FUMIO
