[en] The generation efficiency of correlated photon pairs from a positive-negative index material heterostructure has been investigated by using a rigorous quantum model of spontaneous parametric down-conversion. The mean number of output photon pairs and the signal-field energy spectrum have been calculated. It is shown that the strong confinements of both the pump and signal fields around the resonance state result in a giant enhancement of the correlated photon-pair generation. The generation rate of the correlated photon pair can be improved by several orders of magnitude in the present structure in comparison with those in the corresponding conventional resonant cavity. This means that the present structure can be applied as a highly efficient potential source for entangled photon pairs.