Controls of diffusion and segregation of Si atoms through a thin metal layer from stacked Si structure is one of the effective techniques to grow two dimensional (2D) or ultrathin Si crystals. In this study, an 30 nm-thick Al layer was formed on Si(111) substrate as a crystalline growth template of segregated Si atoms. Si segregation on Al(111) surface with keeping surface flatness was demonstrated by post annealing in N2 ambient at temperature below 500 ºC.