A technique applying the homogenized KrF excimer laser reformation to fabricate Si spheres on the silicon on insulator platform is presented. High-power excimer laser was used to illuminate the Si rods which were fabricated using typical procedures. The Si rods were then melted and reshaped to spheres due to surface tension. This method is capable of fabricating submicrometer Si spheres with extremely smooth surface. Atomic force microscopy was used to reveal the atomic-scale surface smoothness of the fabricated Si spheres. It shows that root-mean-square roughness is smaller than 0.1 nm. In addition, tunneling electron microscopy was used to investigate crystalline property of the Si spheres, showing that single-crystalline Si with lattice plane spacing of about 0.24 nm was formed after the transformation of the Si rod into the sphere.