  It is theoretically demonstrated that the figure of merit ($ZT$) of quantum
dot (QD) junctions can be significantly enhanced when the degree of degeneracy
of the energy levels involved in electron transport is increased. The theory is
based on the the Green-function approach in the Coulomb blockade regime by
including all correlation functions resulting from electron-electron
interactions associated with the degenerate levels ($L$). We found that
electrical conductance ($G_e$) as well as electron thermal conductance
($\kappa_e$) are highly dependent on the level degeneracy ($L$), whereas the
Seebeck coefficient ($S$) is not. Therefore, the large enhancement of $ZT$ is
mainly attributed to the increase of $G_e$ when the phonon thermal conductance
($\kappa_{ph}$) dominates the heat transport of QD junction system. In the
serially coupled double-QD case, we also obtain a large enhancement of $ZT$
arising from higher $L$. Unlike $G_e$ and $\kappa_e$, $S$ is found almost
independent on electron inter-dot hopping strength.
