Method for manufacturing a semiconductor memory cell with a floating gate

Abstract

A method for manufacturing a semiconductor memory cell with a floating gate having a predetermined length includes the steps of: growing a thin oxide layer over a substrate; depositing a polysilicon layer over the thin oxide layer; depositing a silicon nitride layer over the polysilicon layer; masking and etching the nitride layer down to the polysilicon layer so as to form an oxide receiving groove in the nitride layer, the groove being parallel to a longitudinal axis of the floating gate to be formed and being longer than the predetermined width of the floating gate to be formed, and the width of the receiving groove in latitudal axis is equal to the predetermined length of the floating gate, the receiving groove overlapping a floating gate region to be defined on the polysilicon layer; growing a polysilicon oxide layer in the receiving groove; removing the nitride layer; providing a mask which is transverse to the polysilicon oxide layer and which has a width equal to the predetermined length of the floating gate to be formed, the mask covering a portion of the polysilicon oxide layer which is directly above the floating gate region; etching remaining portion of the polysilicon oxide layer not covered by the mask; removing the mask; and etching the polysilicon layer with the portion of the polysilicon oxide layer serving as a mask so as to form the floating gate.