Floating gate and method of fabricating the same

Abstract

A floating gate and fabrication method thereof. A semiconductor substrate is provided, on which a gate dielectric layer, a conducting layer, and a patterned hard mask layer are sequentially formed. The surface of the conducting layer is covered by the patterned hard mask layer to form a gate. The conducting layer is etched to a predetermined depth to form an indentation using the patterned hard mask layer as a mask. The conducting layer is oxidized to form an oxide layer on the surface of the conducting layer. The oxide layer and the conducting layer are etched to form multiple tips using the patterned hard mask layer as a mask.

What is claimed is:  
     
         1 . A floating gate formed on the surface of a semiconductor substrate, comprising: 
 a conductive base having a first top portion and a first bottom portion, wherein an edge of the first top is a first tip, and the first bottom portion contacts to the semiconductor substrate;    a conductive protruding layer protruding from the conductive base, and the conductive protruding layer has a flat top, wherein the conductive protruding layer has a second top portion and a second bottom portion, a edge of the second top portion is a second tip, the second bottom portion is connected to the first top portion, the conductive protruding layer has two concave sidewalls; and    wherein a multiple tip floating gate is composed of the conductive base and the conductive protruding layer.    
     
     
         2 . The floating gate of  claim 1 , wherein the conductive base is a poly layer.  
     
     
         3 . The floating gate of  claim 1 , wherein the conductive protruding layer is a poly layer.  
     
     
         4 . A floating gate formed on the surface of a semiconductor substrate, with a gate dielectric layer formed between the floating gate and the semiconductor substrate, comprising: 
 a base poly layer having a first top portion and a first bottom portion, wherein an edge of the first top portion is a first tip, and the first bottom portion contacts to the gate dielectric layer; and    a protruding poly layer protruding from the base poly layer, and the protruding poly layer has a flat top, wherein the protruding poly layer has a second top portion and a second bottom portion, a edge of the second top portion is a second tip, the second bottom portion contacts the first top portion, the protruding poly layer has two concave sidewalls,    wherein a multiple tip floating gate is composed of the base poly layer and the protruding poly layer.