Patent ID: 7259051

Claim:
A method of forming a floating gate, comprising: providing a substrate; forming a gate dielectric layer on the substrate; forming a first dielectric layer with a trench therein, the trench exposing a top surface of the gate dielectric layer; filling a silicon layer in the trench; putting the above substrate into an etching chamber of an etching process tool; etching portions of the silicon layer to form a tip edge by an etching process comprising hydrogen bromide as a major etching gas with suitable amounts of gases (1) chlorine and/or (2) oxygen/helium, wherein the tip edge angle is controlled by the adjusting the etching parameters of the etching gas compositions and ratios, the etching chamber pressures, and the etching process tool radio frequency powers; forming a second dielectric layer overlying the silicon layer with a tip in the trench; and selectively removing the first dielectric layer to leave the silicon layer covered by the second dielectric layer as a floating gate.