Process for forming a static-random-access memory cell
First Claim
1. A process for forming a static-random-access memory cell comprising the steps of:
- providing a substrate including;
a semiconductor base material having a first conductivity type;
a buried oxide layer overlying the semiconductor base material;
a first doped region overlying the buried oxide layer, wherein the first doped region has a second conductivity type that is opposite the first conductivity type; and
a first semiconductor layer overlying the first doped region and having the first conductivity type;
forming a second doped region, wherein the second doped region;
has the second conductivity type; and
lies within the first semiconductor layer;
forming a first trench extending through the buried oxide layer, first doped region, first semiconductor layer, and second doped region, wherein;
the first trench has a wall surface, a bottom surface, and a central region; and
a channel region of a first transistor lies within the first semiconductor layer adjacent to the wall surface of the first trench;
forming a second semiconductor layer overlying the semiconductor base material within the central region of the first trench, wherein;
the second semiconductor layer has the second conductivity type;
the second semiconductor layer has a wall surface that faces the wall surface of the first trench; and
a channel region of a second transistor lies within the second semiconductor layer and adjacent to the wall surface of the second semiconductor layer;
forming a third doped region lying within the second semiconductor layer and having the first conductivity type;
forming a first gate dielectric layer lying adjacent to the wall surface of the first trench and second semiconductor layer and adjacent to the bottom surface of the first trench outside of the central region of the first trench; and
forming a first conductive member, wherein the first conductive member;
lies at least partially within the first trench and adjacent to the first gate dielectric layer;
laterally surrounds the second semiconductor layer; and
acts as a shared-gate electrode for the first and second transistors.
1 Assignment
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Accused Products
Abstract
An SRAM cell includes a pair of cross-coupled inverters where each inverter includes vertical n-channel and p-channel transistors having a gate electrode that is shared between the transistors that make up each inverter. The gate electrodes for the inverters laterally surround the channel regions of the p-channel load transistors to achieve a relatively high beta ratio without occupying a large amount of substrate surface area. Also, the gate electrodes increase the amount of capacitance of the storage nodes and decreases the soft error rate. The active regions of the latch transistors are electrically isolated from the substrate by a buried oxide layer, thereby decreasing the chances of latch-up.
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Citations
15 Claims
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1. A process for forming a static-random-access memory cell comprising the steps of:
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providing a substrate including; a semiconductor base material having a first conductivity type; a buried oxide layer overlying the semiconductor base material; a first doped region overlying the buried oxide layer, wherein the first doped region has a second conductivity type that is opposite the first conductivity type; and a first semiconductor layer overlying the first doped region and having the first conductivity type; forming a second doped region, wherein the second doped region; has the second conductivity type; and lies within the first semiconductor layer; forming a first trench extending through the buried oxide layer, first doped region, first semiconductor layer, and second doped region, wherein; the first trench has a wall surface, a bottom surface, and a central region; and a channel region of a first transistor lies within the first semiconductor layer adjacent to the wall surface of the first trench; forming a second semiconductor layer overlying the semiconductor base material within the central region of the first trench, wherein; the second semiconductor layer has the second conductivity type; the second semiconductor layer has a wall surface that faces the wall surface of the first trench; and a channel region of a second transistor lies within the second semiconductor layer and adjacent to the wall surface of the second semiconductor layer; forming a third doped region lying within the second semiconductor layer and having the first conductivity type; forming a first gate dielectric layer lying adjacent to the wall surface of the first trench and second semiconductor layer and adjacent to the bottom surface of the first trench outside of the central region of the first trench; and forming a first conductive member, wherein the first conductive member; lies at least partially within the first trench and adjacent to the first gate dielectric layer; laterally surrounds the second semiconductor layer; and acts as a shared-gate electrode for the first and second transistors. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. A process for forming a static-random access memory cell comprising the steps of:
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providing a semiconductor substrate including; a semiconductor base material having a first conductivity type; a buried oxide layer overlying the semiconductor base material; a first doped region overlying the buried oxide layer, wherein the first doped region has a second conductivity type that is opposite the first conductivity type; and a first semiconductor layer overlying the first doped region and having the first conductivity type; forming a second doped region and a third doped region, wherein the second and third doped regions; have the second conductivity type; lie within the first semiconductor layer; and are spaced apart from each other; forming a first trench and a second trench wherein; the first trench extends through the buried oxide layer, first doped region, first semiconductor layer, and the third doped region; the second trench extends through the buried oxide layer, first doped region, first semiconductor layer, and the second doped region; each of the first and second trenches has a wall surface, a bottom surface, and a central region; a channel region of a first latch transistor lies within the first semiconductor layer adjacent to the wall surface of the first trench; and a channel region of a second latch transistor lies within the first semiconductor layer adjacent to the wall surface of the second trench; forming a second semiconductor layer overlying the semiconductor material, wherein; a first portion of the second semiconductor layer is formed within the central region of the first trench and has a wall surface that faces the wall surface of the first trench; a second portion of the second semiconductor layer is formed within the central region of the second trench and has a wall surface that faces the wall surface of the second trench; the second semiconductor layer has the second conductivity type; a channel region of a first load transistor lies adjacent to the wall surface of the first portion; and a channel region of a second load transistor lies adjacent to the wall surface of the second portion; forming a fourth doped region and a fifth doped region, wherein; the fourth doped region lies within the first portion of the second semiconductor layer; the fifth doped region lies within the second portion of the second semiconductor layer; and the fourth and fifth doped regions have the first conductivity type; forming a first gate dielectric layer and a second gate dielectric layer, wherein; the first gate dielectric layer lies adjacent to the wall surfaces of the first trench and the first portion of the second semiconductor layer and adjacent to the bottom surface of the first trench outside of the central region of the first trench; and the second gate dielectric layer lies adjacent to the wall surfaces of the second trench and the second portion of the second semiconductor layer and adjacent to the bottom surface of the second trench outside of the central region of the second trench; forming a first conductive member and a second conductive member, wherein; the first conductive member; lies at least partially within the first trench and adjacent to the first gate dielectric layer; laterally surrounds the first portion of the second semiconductor layer; and acts as a shared-gate electrode for the first latch and first load transistors; and the second conductive member; lies at least partially within the second trench and adjacent to the second gate dielectric layer; laterally surrounds the second portion of the second semiconductor layer; and acts as a shared-gate electrode for the second latch and second load transistors; forming a sixth doped region and a seventh doped region, wherein the sixth and seventh doped regions; have the second conductivity type; lie within the first semiconductor layer; and are spaced apart from each other and the second and third doped regions; and forming at least one third conductive member, wherein the at least one third conductive member; overlies portions of the second, third, sixth, and seventh doped regions, a portion of the first semiconductor layer that lies between the second and sixth doped regions, and another portion of the first semiconductor layer that lies between the third and seventh doped regions; and acts as gate electrodes for access transistors. - View Dependent Claims (10, 11, 12, 13, 14, 15)
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Specification