Semiconductor device having improved bias dependability and method of fabricating same

A method of fabricating a semiconductor device, comprising the steps of:

• a) forming a first insulating layer with a gate insulating region on a semiconductor substrate;
• b) forming a first polysilicon layer on said first insulating layer and said gate insulating region, said first polysilicon layer having a first portion spaced from a second portion which contacts said gate insulating region;
• c) doping an impurity into said first portion of said first polysilicon layer, said impurity having a conductivity type equal to conductivity type of said first polysilicon;
• d) forming a second insulating layer on said first polysilicon layer;
• e) forming a second polysilicon layer on said second insulating layer;
• f) performing a first selective etching process so that a capacitive insulating layer and an upper polysilicon electrode are successively formed on said first portion of the first polysilicon layer, and said second portion of the first polysilicon layer is exposed;
• and
• g) performing a second selective etching process so that said first and second portions of the first polysilicon layer define a lower polysilicon electrode and a gate electrode, respectively.