A first mathematical expression indicating a dependence of SER on an
information storage node diffusion layer area at the same information
storage node voltage Vn is derived with a use of a result of measuring a
relationship between SER and the information storage node diffusion layer
area of a storage circuit or an information holding circuit composed of
MISFET using a plurality of information storage node voltages Vn as a
parameter. Then, a second mathematical expression is derived from the
measurement result by substituting a relationship indicating a dependence
of SER on an information storage node voltage at the same information
storage node diffusion layer area Sc into the first mathematical
expression. SER can be calculated by substituting a desired information
storage node diffusion layer area and a desired information storage node
voltage of a storage circuit or an information holding circuit into the
second mathematical expression.