Abstract: A method of forming a gate structure. A gate oxide layer, a polysilicon layer, a metallic layer and an insulation layer are sequentially formed over a substrate. Using a definite height level to be an etching end point, the insulation layer, the metallic layer and the polysilicon layer are patterned to form a stack structure. A barrier layer is formed over the stack structure. An etching operation is conducted to form a first spacer covering a portion of each sidewall of the stack structure. The etching operation is continued to remove the polysilicon layer outside the first spacer until the gate oxide layer is exposed. A portion of the exposed polysilicon layer on the sidewalls of the stack structure is removed so that a recess structure is formed. A re-oxidation process is conducted to form a re-oxidation layer within the recess structure. A second spacer is formed over the first spacer and the re-oxidation layer.

Abstract: A method of forming a gate structure. A gate oxide layer, a polysilicon layer, a metallic layer and an insulation layer are sequentially formed over a substrate. Using a definite height level to be an etching end point, the insulation layer, the metallic layer and the polysilicon layer are patterned to form a stack structure. A barrier layer is formed over the stack structure. An etching operation is conducted to form a first spacer covering a portion of each sidewall of the stack structure. The etching operation is continued to remove the polysilicon layer outside the first spacer until the gate oxide layer is exposed. A portion of the exposed polysilicon layer on the sidewalls of the stack structure is removed so that a recess structure is formed. A re-oxidation process is conducted to form a re-oxidation layer within the recess structure. A second spacer is formed over the first spacer and the re-oxidation layer.