This document discusses power MOSFETs. It describes that there are two types of MOSFETs: D-MOSFET and E-MOSFET. It then explains different types of power MOSFET structures including planar, VMOS, UMOS, HEXFET, and TrenchMOS. It notes that these structures allow for higher voltage ratings, lower resistance, and better current handling. The document also discusses DMOS and VMOS transistors and their characteristics. Finally, it lists some applications of power MOSFETs such as linear power supplies, switching power supplies, DC-DC converters, and motor control.

1. By
Shaik Hedayath Basha
Assistant Professor
RMK College of Engineering and Technology
Puduvoyal, Chennai.
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*Two types of MOSFET
*D-MOSFET
*E-MOSFET

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*The Flow of current is lateral (Horizontal) in the basic type of
MOSFET.
*The Current flow from Source to Drain (FET Analogy – Ex. Water
flowing from Tank (Source) to Drain with variable Gate Control.
*In Power MOSFET the Current flow Vertically from Source to
Drain or Drain to Source depending upon the biasing.

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* Planar power MOSFET: This is the basic form of power MOSFET. It is good for high
voltage ratings because the ON resistance is dominated by the epi-layer resistance.
This structure is generally used when a high cell density is not needed.
* VMOS: VMOS power MOSFETs have been available for many years. The basic
concept uses a V groove structure to enable a more vertical flow of the current,
thereby providing lower ON resistance levels and better switching characteristics.
Although used for power switching, they may also be used for high frequency small
RF power amplifiers.
* UMOS: The UMOS version of the power MOSFET uses a grove similar to that the
VMOS FET. However the grove has a flatter bottom to it and provides some
different advantages.
* HEXFET: This form of power MOSFET uses a hexagonal structure to provide the
current capability.
* TrenchMOS: Again the TrenchMOS power MOSFET uses a similar basic grove or
trench in the basic silicon to provide better handling capacity and characteristics.
In particular, Trench power MOSFETs are mainly used for voltages above 200 volts
because of their channel density and hence their lower ON resistance.

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*It has very high communication speed
*It has good efficiency at low voltage level.
*It is mostly used as low voltage switch.( less
than 200 Volts)

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*DMOS: Double Diffused Metal Oxide Silicon
*VMOS: Vertical Metal Oxide Silicon

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The DMOS devices uses a double diffusion process.
The n- drift region must be moderately doped so that the
drain breakdown voltage is large.
The thickness of the n-drift region should be thin as possible
to minimize the drain resistance.
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*The V- the shape of power MOSFET is cut to
penetrate from the device surface is almost to the
N+ substrate to the N+, P, and N – layers.
*The N+ layer is the heavily doped layer with a low
resistive material and the N- layer is a lightly
doped layer with the high resistance region.

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*Linear power supplies
*Switching power supplies
*DC-DC converters
*Low voltage motor control