FET Gate Line Shielding Layout to Cut Gate-Drain Capacitance
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Solution Overview
Problem
In semiconductor devices with field effect transistors, the parasitic capacitance between gate and drain electrodes leads to deteriorated characteristics such as gain, due to the proximity of gate lines to drain electrodes, which increases gate-drain capacitance.
Innovation Solution
The implementation of a semiconductor device structure that includes a guard metal layer between the gate and drain electrodes, electrically connected to the source electrode, which suppresses parasitic capacitance by cutting off electric field lines between the gate and drain electrodes, thereby improving the high-frequency characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If gate lines are provided close to drain electrodes for compact layout, then device integration is improved, but parasitic capacitance between gate and drain increases
Solution Approach 1:
A guard metal layer is introduced as an intermediary element positioned between the gate line and the drain electrode. This guard metal layer acts as a shield that intercepts and redirects electric field lines, preventing direct capacitive coupling between the gate and drain. The guard metal layer is electrically connected to a reference potential (typically ground or source), creating an equipotential barrier that reduces the parasitic capacitance effect while allowing the gate line to remain in close proximity to the drain electrode for compact layout.
2Device complexity
If gate lines extend close to drain electrodes for electrical connection, then device complexity is reduced, but high-frequency characteristics deteriorate
Solution Approach 1:
The guard metal layer serves as a mediating structure that allows the gate line to extend close to the drain electrode for simplified routing while simultaneously protecting against parasitic capacitance. By positioning the guard metal layer between the gate line and drain electrode, and connecting it to reference potential, the structure enables compact gate line routing without degrading high-frequency performance.
Solution Approach 2:
The guard metal layer is positioned in advance between the gate line and drain electrode to preemptively counteract the formation of parasitic capacitance. By establishing this protective barrier before the harmful capacitive coupling can develop, the structure prevents high-frequency characteristic deterioration while maintaining simple gate line routing.
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 parasitic capacitance, enhancing the maximum oscillation frequency and overall performance of the FET by minimizing the impact of gate-drain capacitance on the device's characteristics.
Implementation Method 1
parasitic capacitance between gate and drain electrodes leads to deteriorated characteristics such as gain, due to the proximity of gate lines to drain electrodes, which increases gate-drain capacitance
Data Source
AI summary
A semiconductor device includes a substrate, a source electrode, a drain electrode, a first gate electrode extending in a first direction and provided between the source electrode and the drain electrode, a second gate electrode provided in a region between the source electrode and the drain electrode positioned in the first direction from the first gate electrode, a gate pad provided so as to dispose the first gate electrode between the gate pad and the second gate electrode, and electrically connected to the first gate electrode, a first gate line provided above the source electrode, a second gate line provided above the source electrode and extending in a second direction that crosses the first direction, and a first guard metal layer provided between the second gate line and the drain electrode, and having at least a portion provided between the drain electrode and the source electrode.