Monolithic perovskite-silicon tandem solar cells using MoOx hole selective contact silicon cell as bottom structure shows a power conversion efficiency of 5.7%. A thin (15nm in thickness) MoOx contact to n-type Si was used instead of a standard p+ emitter to collect holes and the SiOx/n+ poly-Si structure was applied on the rear of the device for direct tunneling of electrons and blocking holes. With this bottom silicon structure, 14% of devices were manufactured. With this bottom carrier selective silicon cell, tin oxide, and subsequent perovskite structure were deposited to fabricate monolithic tandem solar cells. Monolithic tandem structure without ITO interlayer was also compared to confirm the role of MoOx in tandem cells and this tandem structure shows the power conversion efficiency of 4%. Through this experiment, we have confirmed that the MoOx layer play roles as a passivation layer, hole collecting material, and recombination layer at the same time in the tandem structure.