Recessed MOS Capacitor Structure for Higher Capacitance Density
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Solution Overview
Problem
Conventional MOS capacitors with flat plate-shaped electrodes face challenges in increasing capacity without increasing occupied area, making it difficult to enhance the charge storage capability per unit area.
Innovation Solution
A semiconductor element with a recessed first semiconductor region, an insulation film, and a gate electrode, where the second semiconductor region of the same conductive type supplies carriers, forming a MOS capacitor that expands the electrode area and interface, thereby increasing capacitance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a planar type MOS capacitor with flat plate-shaped electrodes is used, then the structure is simple and easy to manufacture, but the capacity per unit area cannot be increased
Solution Approach 1:
The patent transitions from a two-dimensional planar electrode structure to a three-dimensional structure by forming a recess in the semiconductor substrate and filling it with the electrode material. This vertical expansion into the third dimension increases the electrode surface area without increasing the planar footprint, thereby increasing capacitance per unit area.
Solution Approach 2:
The electrode is nested within the recess formed in the semiconductor substrate. The insulating film is then formed over this nested structure, and the gate electrode is formed over the insulating film. This nested arrangement allows the capacitor components to be stacked vertically, increasing capacity without proportionally increasing the occupied area.
2Quantity of substance
If the capacity of the MOS capacitor is increased by enlarging the electrode area, then the capacity increases, but the occupied area increases proportionally
Solution Approach 1:
Instead of increasing electrode area in the planar direction, the patent increases the effective electrode area by utilizing the vertical dimension through the recess structure. The electrode surface area is expanded within the recess, increasing capacitance without increasing the planar projection area.
3Quantity of substance
If a recess is formed in the first semiconductor region, then the electrode area and interface are expanded increasing capacitance, but the device structure becomes more complex
Solution Approach 1:
The semiconductor substrate is segmented by forming a recess that creates distinct regions: the recessed area containing the electrode and insulating film, and the surrounding flat substrate area. This segmentation allows the capacitor structure to be integrated into the substrate without requiring a completely separate complex structure.
Solution Approach 2:
The recess structure serves multiple functions: it increases the electrode surface area for higher capacitance, provides a confined space for the insulating film, and can be integrated with surrounding circuit structures. The second semiconductor region adjacent to the recess also serves dual purposes as both a structural element and a carrier supply region.
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
The solution effectively increases the capacity of the MOS capacitor per unit area by expanding the semiconductor region and interface, improving high-frequency characteristics and reducing wiring resistance and parasitic inductance.
Implementation Method 1
a MOS capacitor is constituted between the gate electrode and the first semiconductor region
Implementation Method 2
a second semiconductor region that is arranged adjacent to the first semiconductor region on the semiconductor substrate, formed in a same conductive type as the first semiconductor region, and supplies a carrier to the first semiconductor region when the MOS capacitor is charged and discharged
Data Source
AI summary
The capacity of a MOS capacitor is increased. A semiconductor element includes a first semiconductor region, an insulation film, a gate electrode, and a second semiconductor region. The first semiconductor region is arranged on a semiconductor substrate and has a recess on the surface. The insulation film is arranged adjacent to the surface of the first semiconductor region. The gate electrode is arranged adjacent to the insulation film and constitutes a MOS capacitor with the first semiconductor region. The second semiconductor region is arranged adjacent to the first semiconductor region on the semiconductor substrate, formed in the same conductive type as the first semiconductor region, and supplies a carrier to the first semiconductor region when the MOS capacitor is charged and discharged.