This study unveils the anomalous Nernst coefficient enhancement mechanism in ferromagnetic Co/semiconductor Si multilayer films featured by drastically low thermal conductivity unlike conventional ferromagnetic metal/ nonmagnetic metal multilayer films. In a context where a lot of previous studies of multilayer films have discussed the mysterious interface effect, we identified the origin of anomalous Nernst coefficient enhancement effect at the interface by isolating thermoelectric properties of interface layer. It was found that this enhancement effect was attributed to the strengthened interface carrier scatterings. Thanks to this interface effect, Co/Si multilayer films exhibited an order of magnitude higher anomalous Nernst coefficient than Co films, resulting in ~30 times higher thermoelectric power factor. This direct evidence of the interface effect will open an avenue for high-performance thermoelectric materials based on anomalous Nernst effect.