1T/0C RAM cell with a wrapped-around gate device structure

Abstract

A memory device and a method of forming the memory device. The memory device comprises a storage transistor at a surface of a substrate comprising a body portion between first and second source / drain regions, wherein the source / drain regions are regions of a first conductivity type. The storage transistor also comprises a gate structure that wraps at least partially around the body portion in at least two spatial planes. A bit line is connected to the first source / drain region and a word line connected to the gate structure. The memory device does not require an additional capacitive storage element.

Description

FIELD OF THE INVENTION [0001] The present invention relates to memory devices, more specifically to a dynamic random access memory device including a field effect transistor storage device. BACKGROUND OF THE INVENTION [0002] Semiconductor memory, such as a random access memory (RAM), is an essential semiconductor device. A RAM device allows the user to execute both read and write operations on its memory cells. DRAM is a specific category of RAM containing an array of individual memory cells. DRAM devices are the most cost effective high speed memory used with computers and computer systems. Typically, each cell includes a capacitor for holding a charge and a transistor for accessing the charge held in the capacitor. The transistor is often referred to as the access transistor or the transfer device of the DRAM cell. [0003]FIG. 1 illustrates a portion of a DRAM memory circuit containing two neighboring DRAM cells 100. Each cell 100 contains a storage capacitor 104 and an access fiel...

AI Technical Summary

Problems solved by technology

As DRAM devices continue to be scaled down in size, it is difficult to provide capacitors in a small area with sufficient capacitance, typically greater than 30 femtoFarads (fF).

In addition, it is difficult to provide an access transistor with good off-state leakage characteristics for refresh operations and good on-state characteristics to write into the cell.

Such capacitor-less cells, however, can suffer from poor performance characteristics related to retention time, access time, distribution characteristics, and reliability.

In a 1T / 0C DRAM cell, carriers are generated in the substrate bulk to write a “1,” and are pulled out from the substrate bulk to write a “0.” In a 1T / 0C DRAM cell employing a planar SOI device, carrier generation can present problems.

For example, when impact ionization is essential for operation of such a DRAM cell, device reliability can be poor and efficiency can be reduced at higher temperatures due to a decrease in ionization.

Also, a planar device can result in limited operation speed, disturb, and write operations that consume a lot of power because the transistor must be in an on-state.

Further, when the planar SOI devices are scaled to smaller sizes charge storage can be limited due to the reduced active area.

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