Metal Gate Structure of High-Voltage Device and Method for Making the Same

A method for making a metal gate structure of a high-voltage device, comprising:

• step 1, providing a silicon substrate, the silicon substrate being provided with an active region, forming a gate oxide layer on the active region, and forming a dummy gate on the gate oxide layer, wherein the dummy gate is composed of a plurality of polysilicon structures spaced apart from each other;
• step 2, forming a protective layer on sidewalls of the plurality of polysilicon structures and on the gate oxide layer between the polysilicon structures;
• step 3, performing covering with an insulating layer to fill a region between the polysilicon structures, wherein the filled region forms an insulating structure;
• step 4, removing the polysilicon structure to form a groove;
• step 5, forming a metal layer, wherein the metal layer covers the insulating structure and fills the groove;
• and
• step 6:
• polishing a surface of the metal layer, wherein the insulating structure, the protective layer, and the metal layer form a metal gate with a planarized surface.