AII-Si tandem solar cells comprising quantum dot superlattice (ODSL) have attracted much attention. However, a fabrication to realize uniform and controllable OD size (determines band gap (Eg)) and spacing between ODs (generates miniband) in ODSL is still a big challenge. In this study, we created a two-dimensional sub-10nm-Sinano-disk array (2D Si-ND array) with a high-density and well-ordered arrangement using bio-template (Iron-oxide core) as a Φ-7-nm-etching-mask and an advanced etching process that included NF3 treatment and damage-free neutral beam (NB) etching. The 2D Si-ND array shows high photon absorption coefficient (>105 cm -1) and high PL intensity at room temperature owing to high-density 2D SiND (>7×1011 cm-2) and narrow spacing. The Eg and PL emission peaks can be easily controlled by changing the ND thickness. The Eg varied from 2.2 to 1.4 eV. To realize tandem solar cells, we also investigated fabricating stacked NDs, which is to stack the NDs along the 3rd dimension. The NDs were separated by 1-2nm-thick SiO2 that was formed by our developed NB oxidation (NBO) at 300°C. The tunneling current can be controlled by changing the tunneling junction thickness using NBO. Those results support the feasibility of our proposed processes for the high-efficiency all-Si tandem solar cells comprising ODSL.