A
semiconductor integrated circuit device having a switching MISFET, and a
capacitor element formed over the
semiconductor substrate, such as a
DRAM, is disclosed. In a first aspect of the present invention, the
impurity concentration of the
semiconductor region of the switching MISFET to which the
capacitor element is connected is less than the
impurity concentration of semiconductor regions of MISFETs of
peripheral circuitry. In a second aspect, the Y-select
signal line overlaps the lower
electrode layer of the
capacitor element. In a third aspect, a potential
barrier layer, provided at least under the semiconductor region of the switching MISFET to which the capacitor element is connected, is formed by
diffusion of an
impurity for a
channel stopper region. In a fourth aspect, the
dielectric film of the capacitor element is co-extensive with the capacitor
electrode layer over it. In a fifth aspect, the capacitor
dielectric film is a
silicon nitride film having a
silicon oxide layer thereon, the
silicon oxide layer being formed by oxidizing a
surface layer of the
silicon nitride under
high pressure. In sixth and seventh aspects, wiring is provided. In the sixth aspect, an aluminum wiring layer and a protective (and / or barrier) layer are formed by
sputtering in the same vacuum
sputtering chamber without breaking the vacuum between forming the
layers; in the seventh aspect, a
refractory metal, or a
refractory metal suicide QSi.sub.x, where Q is a
refractory metal and 0<x<2, is used as a protective layer, for an aluminum wiring containing an added element (e.g., Cu) to prevent migration.