Method of modulating threshold voltage of a mask ROM
AssigneeMacronix International Co., Ltd.
InventorKuang-Wen Liu
Life of this patent
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Abstract
A method of modulating a threshold voltage of a mask read-only memory, including providing a substrate, providing a source region in the substrate, providing a drain region in the substrate, defining a channel region between the source and drain regions, providing a gate dielectric layer over the substrate, the source region, the drain region and the channel region, providing a gate over the gate dielectric layer, and providing a parasitic capacitor between the gate and the substrate to modulate the threshold voltage of the mask read-only memory, wherein the threshold voltage is inversely proportional to a value of the parasitic capacitor.
Claims19
A method of modulating a threshold voltage of a mask read-only memory, comprising:
- providing a substrate;
- providing a source region in the substrate;
- providing a drain region in the substrate;
- defining a channel region between the source and drain regions;
- providing a gate dielectric layer over the substrate, the source region, the drain region and the channel region;
- providing a gate over the gate dielectric layer;
- and
- providing a parasitic capacitor between the gate and the substrate to modulate the threshold voltage of the mask read-only memory, wherein the threshold voltage is inversely proportional to a value of the parasitic capacitor.
A method of modulating a threshold voltage of a mask read-only memory, comprising:
- providing a substrate;
- providing a source region in the substrate;
- providing a drain region in the substrate;
- defining a channel region between the source and drain regions;
- providing a gate dielectric layer over the substrate, the source region, the drain region and the channel region;
- and
- providing a gate having a gate depletion effect to module the threshold voltage.
A method of forming a mask read-only memory, comprising:
- providing a semiconductor substrate;
- forming a plurality of bit lines in the substrate;
- forming a gate insulation layer over the substrate;
- forming a plurality of polysilicon layers over the gate insulation layer;
- and
- implanting impurity ions into at least one predetermined portion of the plurality of polysilicon layers to modulate a threshold voltage of a memory cell.
Dependencies are inferred from the claim text.