Semiconductor device and method for manufacturing the same

Abstract

A semiconductor device includes a substrate, a dielectric layer, a source region, a drain region, and a metal structure. The substrate has a trench therein, and the dielectric layer is conformally formed over the substrate and the trench. The source region and the least one drain region are in the substrate. The metal structure is filled in the trench and surrounded by the dielectric layer, and the metal structure is disposed between the source region and the drain region. Moreover, the metal structure has a first metal portion and a second metal portion which has a height greater than a height of the first metal portion, and the first metal portion is disposed between the drain region and the second metal portion.

Description

BACKGROUNDField of Invention[0001]The present invention relates to a recessed access device and a method for manufacturing the same.Description of Related Art[0002]Transistor devices are used with semiconductor devices for numerous purposes, and such use is well known. The characteristics of transistor devices are also well known and documented so that further research may improve the transistor devices. For example, in the case of NMOS transistor devices, it is well known that the drive current of an NMOS transistor device will be higher when a high work function gate material is used as opposed to a low work function gate material. The drive current is stronger in a high work function material because the substrate doping can be much lower with a high work function material, resulting in mobility improvement and an improved drive current.[0003]Similar to NMOS transistor devices, access transistor devices used with memory devices, such as DRAM memory, exhibit a higher drive current...

AI Technical Summary

Benefits of technology

The present patent provides a structure that includes a metal structure between a source region and a drain region. The metal structure has two different heights, which helps to control the current flow and prevent gate-induced drain leakage.

Problems solved by technology

However, the use of a high work function material to form an access transistor in a memory device may lead to off-state leakage across the access transistor.

Off-state leakage includes current leakage that occurs when the access transistor is in an “off” state.

The leakage from the drain to the substrate may include both junction leakage and gate-induced drain leakage.

Junction leakage may include Schokley-Read-Hall type junction leakage and is undesirable.

Gate-induced drain leakage (GIDL) is also undesirable.

Recessed access devices (RADs) used as access transistors in memory devices are especially susceptible to gate-induced drain leakage when in an “off” state.

The gate-induced drain leakage of a RAD structure dominates the off-state leakage that occurs with such devices.

Images