Fabricating method of trench gate metal oxide semiconductor field effect transistor

A method for fabricating a trench gate metal oxide semiconductor field effect transistor, the method comprising steps of:

• providing a substrate;
• forming a hard mask layer on the substrate;
• performing an etching process to remove a part of the hard mask layer and forming a trench in the substrate;
• performing an etching back process to remove a part of the hard mask layer;
• forming a conductive layer on the hard mask layer, and filling the polysilicon layer into the trench;
• and
• performing a planarization process to remove the conductive layer by using the hard mask layer as a stop layer.