  A detailed study of the intermediate symmetry breaking scale, via the
renormalization group equations, for a three generation heterotic string model
arising from the N=2 superconformal construction is reported. The numerical
study shows that the model admits a very large intermediate breaking scale
$\op{>}{\sim}1.0\times10^{16}$ GeV. The role of the gauge singlets in this
model is studied, and it is found that these fields play a crucial role in
determining the directions and the scale of the intermediate symmetry breaking.
The importance of the mixing in generation space is also studied. The
generation mixing terms are found to have special effects in the intermediate
symmetry breaking. Remarkably these terms can produce some {\it new} Yukawa
couplings (not present at the Planck scale) through loops. These couplings are
in general very small compared to the ones with non-vanishing tree level values
and thus offer a {\it new} mechanism to solve the lepton/quark mass hierarchy
problem.
