Semiconductor memory device and method of fabricating the same

Abstract

There is provided a method of fabricating a semiconductor memory device including a memory cell having transistor and a capacitor, and a cylindrical accumulation electrode, the method including the steps of (a) forming a first insulating film on a lower interlayer insulating film, (b) forming at least one hole through the first insulating film so that the hole reaches the lower interlayer insulating film, (c) forming a polysilicon layer in the hole so that an upper surface of the polysilicon layer is located lower than an upper surface of the first insulating film, (d) covering the first insulating film and the polysilicon layer with a second insulating film, (e) etching back the second insulating film so that the second insulating film remains only on a sidewall of the first insulating film, and (f) etching the polysilicon layer with the second insulating film being used as a mask so that the polysilicon layer has a thickness different from a thickness of the first insulating film after the polysilicon layer has been etched. The method makes it possible to independently determine thicknesses of a sidewall and a bottom of a cylindrical accumulation electrode, and hence, design the bottom to have a greater thickness than a thickness of the sidewall. This ensures less risk of fall-down of the sidewall of the cylindrical accumulation electrode, higher structural stability, and higher capacity of the cylindrical accumulation electrode.