Method of making SRAM cell with thin film transistor using two polysilicon layers

A method of forming a thin film field effect transistor SRAM device on a semiconductor substrate of a first conductivity type, said substrate having a surface;

• said method comprising the steps as follows:
• forming field oxide regions on portions of said surface of said substrate and forming a first insulating layer on said surface of said semiconductor substrate between said field oxide regions on said semiconductor substrate;
• forming a first portion of a polysilicon layer over said field oxide regions and said first insulating layer,
• forming a buried contact opening through said first portion of a polysilicon layer and said first insulating layer to said surface of said substrate adjacent to one of said field oxide regions exposing a portion of said surface of said semiconductor substrate,
• forming a second portion of said polysilicon layer over said first portion of said polysilicon layer and over said portion of said surface of said substrate to form a buried contact between said second portion and said surface of said substrate,
• doping said polysilicon layer including said first portion and said second portion,
• patterning said polysilicon layer by forming a mask with openings therethrough for patterning said polysilicon layer to form a control gate electrode and to form a conductor from said buried contact, and etching said polysilicon layer to form said control gate electrode and said conductor through said openings in said mask,
• forming doped source/drain regions in said substrate juxtaposed with said control gate electrode,
• forming an interelectrode dielectric layer over said control gate electrode and said conductor,
• forming a gate opening mask for patterning said interelectrode dielectric layer, said gate opening mask having an opening therethrough over said doped source/drain region in said substrate juxtaposed with said buried contact,
• etching said interelectrode dielectric layer through said opening therethrough to form a gate opening therethrough down to said surface of said substrate,
• forming a gate oxide layer on said surface of said substrate through said gate opening,
• forming a semiconductor film over said interelectrode dielectric layer and said surface of said substrate through said gate opening,
• doping said semiconductor film forming a channel region between source/drain regions in said semiconductor film above said gate opening, and above said gate opening of said thin film transistor, with the doped region therebelow comprising the control gate of said thin film transistor.