Semiconductor device having capacitance element and method of producing the same

A semiconductor device having a capacitance element, comprising:

• an element isolation film formed so as to surround an element formation area on a first conductive-type semiconductor substrate;
• a capacitance element formed of a second conductive-type impurity layer formed on a surface of the element formation area,
• an insulation film formed of a pad oxide film formed in the element formation area;
• a cell plate electrode formed on the insulation film;
• a MOSFET composed of a source layer which is formed in the situation that it adjoins the capacitance element and is superimposed on the impurity layer,
• a drain layer constituting a bit line,
• an insulation film constituting a gate insulation film, and
• a gate electrode constituting a word line formed on the insulation film,
• wherein the cell plate electrode and the gate electrode are structured such that a first silicon layer and a second silicon layer which are formed of a pad silicon layers, are stacked on the element formation area, and the second silicon layer constituting the cell plate electrode extends on the element isolation film.