Manufacturing method of split gate structure and split gate structure

Abstract

A manufacturing method of a split gate structure includes steps of forming a mask oxide layer on the substrate, performing photolithography and etching on the mask oxide layer and the substrate, forming a trench, removing the mask oxide layer, forming a bottom oxide layer on a bottom part and a side wall of the trench and a surface of the substrate, forming a silicon nitride layer on the trench, removing a part of the bottom oxide layer, forming a gate oxide layer on part of the side wall and the surface, forming a gate poly layer on the trench, removing the silicon nitride layer, forming an inter-poly oxide layer on the gate poly layer, and forming a shield poly layer on the trench, thereby benefiting the increasing of the thickness of the inter-poly oxide layer, so that the advantages of improving the characteristics of the split gate structure are achieved.