DRAM process with improved poly-to-poly capacitor
First Claim
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1. A method of making an integrated semiconductor device including an array of memory cells, comprising the steps of:
- providing a substrate having a first device area and a second device area;
forming field isolation layers adjacent to said first device area;
forming a first conductive layer separated from said first device area by a first gate insulating layer;
forming source and drain regions in said substrate on opposing sides of said first conductive layer;
forming a second conductive layer in conductive contact with said source;
forming a first dielectric layer on the surface of said second conductive layer, said first dielectric layer being an oxidation barrier;
oxidizing the surface of said substrate at said second device area to form a second dielectric layer, said first dielectric layer preventing the oxidation of said second conductive layer; and
forming a third conductive layer on said first and second dielectric layers.
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Abstract
The present invention teaches a new method for fabrication of DRAM cells having an upper capacitor plate over the polysilicon storage gate. To provide a very high specific capacitance and very good integrity between the first poly storage gate and the (second or third poly) upper capacitor plate, the dielectric is formed as an oxide/nitride composite which is then reoxidized. This provides the advantages of high dielectric integrity, high specific capacitance, uniformity and reproducibility.
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13 Claims
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1. A method of making an integrated semiconductor device including an array of memory cells, comprising the steps of:
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providing a substrate having a first device area and a second device area; forming field isolation layers adjacent to said first device area; forming a first conductive layer separated from said first device area by a first gate insulating layer; forming source and drain regions in said substrate on opposing sides of said first conductive layer; forming a second conductive layer in conductive contact with said source; forming a first dielectric layer on the surface of said second conductive layer, said first dielectric layer being an oxidation barrier; oxidizing the surface of said substrate at said second device area to form a second dielectric layer, said first dielectric layer preventing the oxidation of said second conductive layer; and forming a third conductive layer on said first and second dielectric layers. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13)
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