Memory cell and memory array select transistor
A semiconductor metal-oxide-semiconductor field effect transistor (MOSFET) with increased on-state current obtained through a parasitic bipolar junction transistor (BJT) of the MOSFET. Methods of operating the MOSFET as a memory cell or a memory array select transistor are provided.
1. A semiconductor memory array comprising:
a plurality of semiconductor devices configured to function as a memory select transistor with increased on-state drain current; wherein each of said semiconductor devices comprises:
a substrate having a first conductivity type selected from p-type conductivity type and n-type conductivity type;
a buried layer having a second conductivity type selected from said p-type conductivity type and said n-type conductivity type and being different from said first conductivity type;
a body having said first conductivity type;
a source region and a drain region each having said second conductivity type and being separated by said body;
a gate positioned in between said source region and said drain region;
a charge trap layer containing a substantial number of charge trap centers that may absorb excess majority carrier, said charge trap layer contacting at least one of said source region and said drain region; and
an insulating layer comprising an STI contacting said charge trap layer;
wherein said semiconductor device is configured to function as a select transistor for at least one memory element connected to said drain region or said source region, wherein a state of said at least one memory element is determined by a resistivity of said at least one memory element.
2. The semiconductor memory array of claim 1 , wherein an amount of on-state drain current enhancement of said semiconductor device functioning as said memory select transistor connected to said at least one memory element is governed by an amount of voltage applied to said buried layer.
3. The semiconductor memory array of claim 1 , wherein a relatively low voltage applied to said buried layer governs said semiconductor device to function as a conventional MOSFET (metal-oxide-semiconductor field effect transistor);
wherein a relatively high voltage applied to said buried layer governs said semiconductor device to a single transistor latch state having at least two stable states at gate voltage of 0 V; and
wherein said semiconductor device is configured to have a relatively intermediate high voltage applied to said buried layer higher than said relatively low voltage and lower than said relatively high voltage, but sufficient to turn on a vertical bipolar junction transistor (BJT) formed by said buried layer, said body and said source region, and to turn on a lateral BJT formed by said source region, said body and said drain region, resulting in increased on-state drain current at high gate voltage, to cause said semiconductor device to function as said select transistor.
4. The semiconductor memory array of claim 3 , wherein said on-state drain current comprises a sum of current from a MOS transistor formed by said source region, said gate and said drain region, and current from said lateral BJT.
5. The semiconductor memory array of claim 1 , further comprising a buried layer tap connected to said buried layer.
6. The semiconductor memory array of claim 1 , wherein said semiconductor device is FinFET, wherein said body comprises a fin structure extending perpendicularly from said substrate.
7. The semiconductor memory array of claim 1 , wherein said charge trap layer directly contacts at least one of said source region and said drain region.
8. The semiconductor memory array of claim 1 , wherein said charge trap layer indirectly contacts at least one of said source region and said drain region via a thin interfacial oxide layer.
9. The semiconductor memory array of claim 1 , further comprising a metal silicide junction located at at least one of: a location between said source region and said body, and a location between said drain region and said body.
10. The semiconductor memory array of claim 1 , further comprising an energy band offset region located at at least one of: a location between said source region and said body, and a location between said drain region and said body.
11. The semiconductor memory array of claim 10 , wherein said energy band offset region comprises a valence band offset material.
12. The semiconductor memory array of claim 1 , further comprising a recombination center located at at least one of: a location between said source region and said body, and a location between said drain region and said body.
13. The semiconductor memory array of claim 12 , wherein said recombination center is formed by doping said at least one location with deep level impurities.
14. The semiconductor memory array of claim 13 , wherein said deep level impurities comprise at least one of gold or platinum.
15. The semiconductor memory array of claim 12 , wherein said recombination center is formed by introducing crystallinity damage through ion implantation.
16. The semiconductor memory array of claim 15 , wherein ions used for said ion implantation are selected from at least one of the group consisting of: Si ions, Ge ions and Ar ions.
17. The semiconductor memory array of claim 1 , wherein said at least one memory element comprises resistive switching memory (RRAM), phase change memory (also known as PCM, PRAM, PCRAM), Chalcogenide memory (CRAM), or magnetoresistive memory (MRAM).
18. The semiconductor memory array of claim 1 , in combination with at least a second said semiconductor device configured to function as a memory select transistor, wherein at least two of said memory select transistors are connected to one said memory element for multi-port operation.
19. The semiconductor memory array of claim 1 , wherein at least two of said memory elements are connected to one said memory select transistor for 1T-nM architecture.
20. The semiconductor memory array of claim 19 , wherein said memory elements are three-dimensionally stacked.