What is a MOS Capacitor?

Encyclopedia
08/26/2024


What is a MOS Capacitor?


MOS Capacitor Defined


MOS stands for Metal Oxide Semiconductor. An MOS capacitor comprises a semiconductor body or substrate, an insulator, and a metal gate. Typically, the gate is made from heavily doped n+ poly-silicon that functions like metal. Silicon dioxide (SiO2) serves as the dielectric material between the capacitor plates, where the metal and semiconductor layers act as the two plates.

 

cefcfa35c64cd4a67a0c3a16d7d938dd.jpeg

 

The capacitance of an MOS capacitor varies with the voltage applied to its gate terminal, with the body typically grounded during this application.


The flat band voltage is an important term related to the MOS capacitor. It is defined as the voltage at which there is no charge on the capacitor plates and hence there is no static electric field across the oxide. An applied positive gate voltage larger than the flat band voltage (Vgb > Vfb) then positive charge is induced on the metal (poly silicon) gate and negative charge in the a title=”Theory of Semiconductor” href=”/theory-of-semiconductor/”>semiconductor. The only negative charged electrons are available as negative charges and they accumulate at the surface. This is known as surface accumulation.

 


bc5b4907ac2d336633a970a1ed5f8c1e.jpeg

 


If the applied gate voltage is lower than the flat band voltage (Vgb < Vfb) then a negative charge is induced at the interface between the poly-silicon gate and the oxide and positive charge in the semiconductor.

 


This is only possible by pushing the negatively charged electrons away from the surface exposing the fixed positive charges from donors. This is known as surface depletion.

 


While the MOS capacitor is not extensively used alone, it is integral to MOS transistors, which are the most widely used semiconductor devices.

 


d57274ad8005f45726ee9c1be17fce6d.jpeg

 


The typical capacitance-voltage characteristics of a MOS capacitor with n-type body is given below,

 


Capacitance vs. Gate Voltage (CV) diagram of a MOS Capacitor. The flatband voltage (Vc-v curve of mos capacitorfb) separates the Accumulation region from the Depletion region. The threshold voltage (Vth) separates the depletion region from the inversion region.

 


0fa9bd6b18f12d389bc7cd5a22da99c8.jpeg


Encyclopedia

The Electricity Encyclopedia is dedicated to accelerating the dissemination and application of electricity knowledge and adding impetus to the development and innovation of the electricity industry.

Does a grid-connected inverter need a grid to operate?
Does a grid-connected inverter need a grid to operate?
Grid-connected inverters do need to be connected to the grid to function properly. These inverters are designed to convert direct current (DC) from renewable energy sources, such as solar photovoltaic panels or wind turbines, into alternating current (AC) that synchronizes with the grid in order to feed power into the public grid. Here are some of the key features and operating conditions of grid-connected inverters:The basic working principle of grid-connected inverterThe basic working principl
Encyclopedia
09/24/2024
Advantages of infrared generator
Advantages of infrared generator
Infrared generator is a kind of equipment that can produce infrared radiation, which is widely used in industry, scientific research, medical treatment, security and other fields. Infrared radiation is an invisible electromagnetic wave with a wavelength between visible light and microwave, which is usually divided into three bands: near infrared, middle infrared and far infrared. Here are some of the main advantages of infrared generators:Non-contact measurement No contact: The infrared generato
Encyclopedia
09/23/2024
What is a Thermocouple?
What is a Thermocouple?
What is a Thermocouple?Thermocouple DefinitionA thermocouple is a device that converts temperature differences into an electric voltage, based on the principle of the thermoelectric effect. It is a type of sensor that can measure temperature at a specific point or location. Thermocouples are widely used in industrial, domestic, commercial, and scientific applications due to their simplicity, durability, low cost, and wide temperature range.Thermoelectric EffectThe thermoelectric effect is the ph
Encyclopedia
09/03/2024
What is a Resistance Temperature Detector?
What is a Resistance Temperature Detector?
What is a Resistance Temperature Detector?Resistance Temperature Detector DefinitionA Resistance Temperature Detector (also known as a Resistance Thermometer or RTD) is an electronic device used to determine the temperature by measuring the resistance of an electrical wire. This wire is referred to as a temperature sensor. If we want to measure temperature with high accuracy, an RTD is the ideal solution, as it has good linear characteristics over a wide range of temperatures. Other common elect
Encyclopedia
09/03/2024
Inquiry
Download
Experts Electrical is dedicated to serving the personnel in the global power industry.
Join Experts Electrical, not only can you discover power equipment and power knowledge, but also canhnd like - minded friends!