  We use the QCD sum rules to evaluate the form factors associated with the
semileptonic decays of $D_s$ and $D$ mesons into $f_0(980)$. We consider the
$f_0(980)$ meson as a quark-antiquark state with a mixture of strange and light
components. The decay rates are evaluated in terms of the mixing angle. Using
the same form factors to evaluate nonleptonic decays in the framework of the
factorization approximation we conclude that the importance of the light quarks
in $f_0(980)$ is not negligible.
