ONLINE ELECTRICAL ENGINEERING STUDY SITE

MOS Capacitor | MOS Capacitance C V Curve

The acronym MOS stands for Metal oxide semiconductor. An MOS capacitor is made of a semiconductor body or substrate, an insulator and a metal electrode called a gate. Practically the metal is a heavily doped n+ poly-silicon layer which behaves as a metal layer. The dielectric material used between the capacitor plates is silicon dioxide (SiO2). The metal acts as one plate of the capacitor and the semiconductor layer which may be n-type or p-type acts as another plate.MOS capacitor structure The capacitance of the MOS capacitor depends upon the voltage applied on the gate terminal. Usually the body is grounded when the gate voltage is applied.

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 semiconductor. The only negative charged electrons are available as negative charges and they accumulate at the surface. This is known as surface accumulation. MOS capacitor structure 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. mos The MOS capacitor is not a widely used device in itself. However, it is part of the MOS transistor which is by far the most widely used semiconductor device.

The typical capacitance-voltage characteristics of a MOS capacitor with n-type body is given below, c-v curve of mos capacitor Capacitance vs. Gate Voltage (CV) diagram of a MOS Capacitor. The flatband voltage (Vfb) separates the Accumulation region from the Depletion region. The threshold voltage (Vth) separates the depletion region from the inversion region.




Closely Related Articles MOSFET | Working Principle of p-channel n-channel MOSFETMOSFET CircuitsApplications of MOSFETMOSFET as a SwitchMOSFET CharacteristicsPower MOSFETMore Related Articles Op-amp | Working Principle of Op-ampAmplifier Gain | Decibel or dB GainIntegrated Circuits | Types of ICRegulated Power SupplyLaser | Types and Components of LaserWork FunctionMobility of Charge CarrierWhat are Photo Electrons? Electron volt or eVEnergy Quanta | Development of Quantum Physics Schottky EffectHeisenberg Uncertainty PrincipleSchrodinger Wave Equation and Wave FunctionCyclotron Basic Construction and Working PrincipleSinusoidal Wave SignalCommon Emitter AmplifierRC Coupled AmplifierDifferential AmplifierWave Particle Duality PrincipleSpace ChargeInverting AmplifierVacuum Diode History Working Principle and Types of Vacuum DiodePN Junction Diode and its CharacteristicsDiode | Working and Types of DiodeDiode CharacteristicsHalf Wave Diode RectifierFull Wave Diode RectifierDiode Bridge RectifierWhat is Zener Diode?Application of Zener DiodeLED or Light Emitting DiodePIN Photodiode | Avalanche PhotodiodeTunnel Diode and its ApplicationsGUNN DiodeVaractor DiodeLaser DiodeSchottky DiodePower DiodesDiode ResistanceDiode Current EquationIdeal DiodeReverse Recovery Time of DiodeDiode TestingHalf Wave RectifiersFull Wave RectifiersBridge RectifiersClamping CircuitTheory of SemiconductorIntrinsic SemiconductorExtrinsic SemiconductorsEnergy Bands of SiliconDonor and Acceptor Impurities in Semiconductor Conductivity of SemiconductorCurrent Density in Metal and Semiconductor Intrinsic Silicon and Extrinsic SiliconP Type SemiconductorN Type SemiconductorP N Junction Theory Behind P N JunctionForward and Reverse Bias of P N JunctionZener BreakdownAvalanche BreakdownHall Effect Applications of Hall EffectGallium Arsenide SemiconductorSilicon SemiconductorTypes of TransistorsBipolar Junction Transistor or BJTBiasing of Bipolar Junction Transistor or BJTTransistor BiasingTransistor CharacteristicsCurrent Components in a TransistorTransistor Manufacturing TechniquesApplications of Bipolar Junction Transistor or BJT | History of BJTTransistor as a SwitchTransistor as an AmplifierJFET or Junction Field Effect Transistorn-channel JFET and p-channel JFETApplications of Field Effect TransistorDIAC Construction Operation and Applications of DIACTRIAC Construction Operation and Applications of TRIACPhototransistorNew Articles Ring CounterDischarging a CapacitorCharging a CapacitorElectric PotentialParity GeneratorElectric Flux