Memory cell with a vertical transistor and fabrication method thereof
First Claim
1. A memory cell with a vertical transistor, comprising:
- a semiconductor silicon substrate comprising a deep trench, in which the deep trench comprises a first sidewall region and a second sidewall region;
a first insulating layer formed overlying the first sidewall region;
a second insulating layer formed overlying the second sidewall region, in which the thickness of the first insulating layer is larger than the thickness of the second insulating layer;
a gate electrode layer sandwiched between the first insulating layer and the second insulating layer; and
a buried strap out-diffusion region formed in the substrate adjacent to the second sidewall region, in which the buried strap out-diffusion region is located near the lower portion of the second insulating layer.
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Abstract
A memory cell with a vertical transistor has a semiconductor silicon substrate with a deep trench, in which the deep trench has a first sidewall region and a second sidewall region. A first insulating layer is formed overlying the first sidewall region. A second insulating layer is formed overlying the second sidewall region, in which the thickness of the first insulating layer is larger than the thickness of the second insulating layer. A gate electrode layer is sandwiched between the first insulating layer and the second insulating layer. A buried strap out-diffusion region is formed in the substrate adjacent to the second sidewall region, in which the buried strap out-diffusion region is located near the lower portion of the second insulating layer.
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Citations
28 Claims
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1. A memory cell with a vertical transistor, comprising:
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a semiconductor silicon substrate comprising a deep trench, in which the deep trench comprises a first sidewall region and a second sidewall region;
a first insulating layer formed overlying the first sidewall region;
a second insulating layer formed overlying the second sidewall region, in which the thickness of the first insulating layer is larger than the thickness of the second insulating layer;
a gate electrode layer sandwiched between the first insulating layer and the second insulating layer; and
a buried strap out-diffusion region formed in the substrate adjacent to the second sidewall region, in which the buried strap out-diffusion region is located near the lower portion of the second insulating layer. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. A fabrication method for a memory cell with a vertical transistor, comprising the steps of:
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providing a semiconductor silicon substrate comprising a deep trench, in which the deep trench comprises a first sidewall region and a second sidewall region;
forming a first buried strap out-diffusion region and a second buried strap out-diffusion region in the substrate, in which the first buried strap out-diffusion region is adjacent to the first sidewall region of the deep trench, and the second buried strap out-diffusion region is adjacent to the second sidewall region of the deep trench;
forming a shielding layer to cover the second sidewall region of the deep trench;
using the shielding layer as a hard mask and performing an ion implantation process on the first sidewall region of the deep trench;
removing the shielding layer;
forming a first insulating layer on the first sidewall region of the deep trench, and forming a second insulating layer on the second sidewall region of the deep trench, in which the thickness of the first insulating layer is larger than the thickness of the second insulating layer; and
forming a gate electrode layer in the deep trench, in which the gate electrode layer is sandwiched between the first insulating layer and the second insulating layer;
wherein, the second buried strap out-diffusion region is located adjacent to the lower portion of the second insulating layer; and
wherein, the second insulating layer contributes to a normal threshold voltage along the second sidewall region for turning on the vertical transistor. - View Dependent Claims (11, 12, 13, 14)
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15. A memory cell with a vertical transistor, comprising:
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a semiconductor silicon substrate comprising a deep trench, in which the deep trench comprises a first sidewall region and a second sidewall region;
a first collar dielectric layer formed overlying the first sidewall region;
a second collar dielectric layer formed overlying the second sidewall region;
a conductive layer formed in the deep trench and sandwiched by the first collar dielectric layer and the second collar dielectric layer, in which the conductive layer adjacent to the first sidewall region is partially covered by the first collar dielectric layer, and the conductive layer adjacent to the second sidewall region is fully covered by the second collar dielectric layer;
a top insulating layer formed overlying the conductive layer; and
a gate electrode layer sandwiched between the first insulating layer and the second insulating layer;
a buried strap out-diffusion region formed in the substrate adjacent to the first sidewall region, in which the buried strap out-diffusion region is located near the conductive layer;
a first insulating layer formed over the top insulating layer and overlying the first sidewall region of the deep trench;
a second insulating layer formed over the top insulating layer and overlying the second collar dielectric layer on the second sidewall region of the deep trench; and
a gate electrode layer formed in the deep trench and sandwiched by the first insulating layer and the second insulating layer. - View Dependent Claims (16, 17, 18, 19, 20, 21)
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22. A fabrication method for a memory cell with a vertical transistor, comprising the steps of:
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providing a semiconductor silicon substrate comprising a deep trench, in which the deep trench comprises a first sidewall region and a second sidewall region;
forming a first collar dielectric layer on the first sidewall region of the deep trench;
forming a second collar dielectric layer on the second sidewall region of the deep trench;
forming a first conductive layer in the deep trench, in which the first conductive layer is sandwiched by the first collar dielectric layer and the second dielectric layer;
forming a shielding layer to cover the second collar dielectric layer on the second sidewall region;
using the shielding layer as a hard mask and removing the first collar dielectric layer until the top of the first conductive layer protrudes from the top of the first collar dielectric layer;
removing the shielding layer;
forming a second conductive layer overlying the first conductive layer and the first collar dielectric layer, in which the second conductive layer adjacent to the second sidewall region is fully covered by the second collar dielectric layer;
forming a top insulating layer overlying the second conductive layer;
forming a buried strap out-diffusion region in the substrate adjacent to the first sidewall region of the deep trench, in which the buried strap out-diffusion region is located near the second conductive layer;
forming a first insulating layer overlying the first sidewall region of the deep trench;
forming a second insulating layer overlying the second collar dielectric layer on the second sidewall region; and
forming a gate electrode layer in the deep trench and sandwiched by the first insulating layer and the second insulating layer. - View Dependent Claims (23, 24, 25, 26, 27, 28)
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Specification