Method of forming memory cell with built-in erasure feature
First Claim
1. A process for fabricating a semiconductor memory device, comprising the steps of:
- forming a plurality of insulation regions on a semiconductor substrate to define at least one active region on the substrate;
forming a first insulating layer on said active region;
forming a patterned first silicon layer on a portion of said first insulating layer;
forming a patterned second insulating layer overlying at least a portion of said first silicon layer;
forming a recess in said first insulating layer underneath said first silicon layer by removing portions of said first insulating layer between said first silicon layer and said substrate, said recess exposing portions of said substrate and said first silicon layer;
forming a patterned third insulating layer on said exposed portions of said substrate and said first silicon layer, said third insulating layer partially filling said recess; and
forming a patterned second silicon layer covering at least a portion of said third insulating layer and further filling said recess, wherein said second silicon layer includes at least one of a sharp tip and a wedge filling said recess.
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Accused Products
Abstract
A method of fabricating an E2 PROM or a flash memory cell having a sharp tip or thin wedge at one of its gates, e.g., the floating gate, for the erasure of electrical charges stored in the floating gate. A recess is formed between a first polysilicon gate and the substrate by removing portions of an insulating layer interposed between the first gate and the substrate. Another insulating layer, e.g., thermal oxide, is formed on the exposed portions of the first gate and the substrate, and partially fills the recess. A second polysilicon layer is formed on the thermal oxide and patterned to form a floating gate. The partially filled recess causes a sharp polysilicon tip or thin wedge to be formed as part of the floating gate. This sharp tip or thin wedge can generate a high electrical field that facilitates the removal of the stored electrical charges from the floating gate.
42 Citations
17 Claims
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1. A process for fabricating a semiconductor memory device, comprising the steps of:
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forming a plurality of insulation regions on a semiconductor substrate to define at least one active region on the substrate; forming a first insulating layer on said active region; forming a patterned first silicon layer on a portion of said first insulating layer; forming a patterned second insulating layer overlying at least a portion of said first silicon layer; forming a recess in said first insulating layer underneath said first silicon layer by removing portions of said first insulating layer between said first silicon layer and said substrate, said recess exposing portions of said substrate and said first silicon layer; forming a patterned third insulating layer on said exposed portions of said substrate and said first silicon layer, said third insulating layer partially filling said recess; and forming a patterned second silicon layer covering at least a portion of said third insulating layer and further filling said recess, wherein said second silicon layer includes at least one of a sharp tip and a wedge filling said recess. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17)
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Specification