Abstract: A P channel MIS type semiconductor device have P type source and drain regions formed in a N type semiconductor substrate. Each source and drain regions are constructed the low and high impurity concentration layers. Channel side edges of the low concentration impurity layers arranged inside of the high concentration impurity layers. These double layer source and drain structure prevent the off set gate construction and the parasitic resistance.

Abstract: A semiconductor integrated circuit device is disclosed which has an MOSFET with a lightly doped drain or LLD structure. A gate electrode layer is insulatively provided above a semiconductor substrate of p conductivity type. Source and drain layers of n conductivity type are formed in the substrate in such a manner as to be substantially self-aligned with the gate electrode. Each of these source and drain layers is comprised of a heavily doped diffusion layer and a lightly doped diffusion layer. The n- diffusion layer is deep enough to fully surround the heavily doped layer in the substrate. The n- diffusion layer has a step-like cross-section, whereby the effective channel length of MOSFET is increased inside the substrate to increase the punch-through voltage level.