The present application provides a semiconductor structure and a manufacturing method of the semiconductor structure. A substrate is provided, wherein the substrate includes a plurality of pillars, and a top surface of each of the plurality of pillars is a substantially planar surface. A first oxide layer is formed over the substrate conformal to the pillars, wherein the formation of the first oxide layer includes oxidizing top corners of the pillars, thereby causing the top surface of each of the plurality of pillars to become a convex surface. A first dielectric layer is formed among the pillars, wherein the first oxide layer above the plurality of pillars is partially exposed through the first dielectric layer. A planarization is performed on the pillars to partially or entirely remove the convex surface.