Process for manufacturing a semiconductor wafer, a semiconductor wafer, process for manufacturing a semiconductor integrated circuit device, and semiconductor integrated circuit device

A method of manufacturing a semiconductor integrated circuit device, comprising steps of:

• forming an epitaxial layer of a first conductivity type on a semiconductor substrate having a first conductivity type and having a first impurity concentration at a whole of said principal surface of said semiconductor substrate, such that said epitaxial layer is formed on said principal surface of said first impurity concentration, wherein a thickness of said epitaxial layer is within a range of 0.3 μm to 5 μm;
• forming a well region in said epitaxial layer by introducing an impurity in said epitaxial layer through a surface of said epitaxial layer;
• forming a gate oxide film of an MISFET on a surface of said epitaxial layer;
• forming a gate electrode of said MISFET on said gate oxide film on said well region;
• forming semiconductor regions in said epitaxial layer serving as a source region and a drain region of said MISFET;
• and
• forming a capacitor element electrically coupled to one of said semiconductor regions,
• wherein said first impurity concentration is lower than an impurity concentration of a portion of said well region where a channel region of said MISFET is formed.