Semiconductor Gate Dielectric Segmentation for Leakage Reduction
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Solution Overview
Problem
In semiconductor devices with high-dielectric-constant gate dielectrics, the reduction of equivalent oxide thickness (EOT) leads to increased electric field intensity and leakage current, resulting in higher power consumption and limited operation speed due to increased parasitic capacitance.
Innovation Solution
A semiconductor device structure is implemented where a dielectric film with lower permittivity than the high-dielectric-constant material is formed on the end surface of the gate dielectric near the drain, reducing electric field concentration and parasitic capacitance, comprising a semiconductor substrate, source and drain regions, a channel region, a first dielectric film, a high-dielectric-constant second film, and a lower permittivity third film on the end surface of the second film.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the equivalent oxide thickness (EOT) of the gate dielectric is reduced to enhance electrical characteristics, then the gate length can be miniaturized and operation speed improved, but leakage current due to direct tunnel current increases and power consumption rises
Solution Approach 1:
The gate dielectric is segmented into multiple layers with different dielectric constants. A high-dielectric-constant layer (first dielectric film) is positioned near the channel region to maintain strong electric field control, while a low-dielectric-constant layer (second dielectric film) is positioned near the drain region to reduce electric field intensity and leakage current. This segmentation allows simultaneous optimization of both speed and power consumption.
Solution Approach 2:
Different regions of the gate dielectric are assigned different dielectric properties according to local requirements. The high-k material is concentrated where strong field control is needed (near channel), while low-k material is used where field reduction is beneficial (near drain). This local differentiation resolves the contradiction by optimizing each region's contribution to overall device performance.
2Power
If the equivalent oxide thickness (EOT) of the gate dielectric is reduced to increase current drive capability, then transistor current increases, but parasitic capacitance increases and operation speed is limited
Solution Approach 1:
The gate dielectric is divided into high-k and low-k regions to separately optimize current drive and speed. The high-k portion near the channel provides strong capacitive coupling for high current drive, while the low-k portion near the drain reduces parasitic capacitance to enable faster operation. This segmentation breaks the traditional trade-off between power and speed.
Solution Approach 2:
The gate dielectric uses a composite structure combining materials with different dielectric constants in a single continuous layer. This composite approach allows the dielectric to simultaneously provide high capacitance where needed and low parasitic capacitance where needed, resolving the contradiction between current drive capability and operation speed.
3Loss of energy
If a high-dielectric-constant material is used as gate dielectric to reduce EOT, then physical thickness can be increased to reduce leakage current, but electric field intensity increases and causes deterioration in carrier mobility
Solution Approach 1:
The gate dielectric is segmented into a high-k layer near the channel and a low-k layer near the drain. The high-k layer provides thickness increase for leakage reduction, while the low-k layer near the drain prevents excessive electric field intensity that would harm carrier mobility. This segmentation allows both benefits to coexist.
Solution Approach 2:
The dielectric constant is optimized locally: high-k material is placed where thickness increase is beneficial (near channel for leakage reduction), while low-k material is placed where electric field control is critical (near drain for mobility preservation). This local quality differentiation resolves the contradiction between leakage reduction and mobility maintenance.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This configuration reduces leakage current and parasitic capacitance, thereby lowering power consumption and enhancing operation speed by mitigating electric field intensity and capacitance issues.
Implementation Method 1
the electric field intensity in the semiconductor substrate 101 reaches its peak immediately below the end surface of the gate electrode 105 near the drain region 108 (GD)
Implementation Method 2
a dielectric film having a lower permittivity than a high-dielectric-constant material forming a gate dielectric is provided on at least the end surface of the gate dielectric near a drain
Implementation Method 3
the parasitic capacitance of the transistor increases with a decrease in the EOT, this prevents the operation speed of devices from increasing
Data Source
AI summary
A semiconductor device includes: a semiconductor substrate; a source region and a drain region formed in the upper part of the semiconductor substrate so as to be spaced; a channel region formed in a part of the semiconductor substrate between the source region and the drain region; a first dielectric film formed on the channel region of the semiconductor substrate; a second dielectric film formed on the first dielectric film and having a higher permittivity than the first dielectric film; a third dielectric film formed on at least an end surface of the second dielectric film near the drain region out of end surfaces of the second dielectric film near the source and drain regions; and a gate electrode formed on the second dielectric film and the third dielectric film.