At least not less than one capacitor formation trench providing an uneven surface
is formed on the surface of a capacitor formation region. Thus, the surface area
of a capacitor is increased, which enables improvement of the capacitance of the
capacitor per unit area. Further, by forming the capacitor formation trench and
an element formation trench that are formed in the surface of the semiconductor
substrate by the same step, it is possible to simplify the manufacturing process.
Whereas, a dielectric film of the capacitor in the capacitor formation region and
a high-voltage gate insulating film in a MISFET formation region are formed by
the same step; alternatively, the dielectric film of the capacitor in the capacitor
formation region and a memory gate interlayer film between a polysilicon layer
and a polysilicon layer in the memory cell formation region are formed by the same step.