In electronics

Electronics

Electronics is the branch of science, engineering and technology that deals with electrical circuits involving active electrical components such as vacuum tubes, transistors, diodes and integrated circuits, and associated passive interconnection technologies...

, a short-channel effect is an effect whereby a MOSFET

MOSFET

The metal–oxide–semiconductor field-effect transistor is a transistor used for amplifying or switching electronic signals. The basic principle of this kind of transistor was first patented by Julius Edgar Lilienfeld in 1925...

, in which the channel length is the same order of magnitude

Order of magnitude

An order of magnitude is the class of scale or magnitude of any amount, where each class contains values of a fixed ratio to the class preceding it. In its most common usage, the amount being scaled is 10 and the scale is the exponent being applied to this amount...

 as the depletion-layer widths (xdD, xdS) of the source and drain junction, behaves differently from other MOSFETs.

As the channel length L is reduced to increase both the operation speed and the number of
components per chip, the so-called short-channel effects arise.


The short-channel effects are attributed to two physical phenomena:

1. the limitation imposed on electron
   Electron
   The electron is a subatomic particle with a negative elementary electric charge. It has no known components or substructure; in other words, it is generally thought to be an elementary particle. An electron has a mass that is approximately 1/1836 that of the proton...
   
    drift characteristics in the channel,
2. the modification of the threshold voltage
   Threshold voltage
   The threshold voltage of a MOSFET is usually defined as the gate voltage where an inversion layer forms at the interface between the insulating layer and the substrate of the transistor. The purpose of the inversion layer's forming is to allow the flow of electrons through the gate-source junction...
   
    due to the shortening channel length.

In particular five different short-channel effects can be distinguished:

1. drain-induced barrier lowering and punchthrough
2. surface scattering
3. velocity saturation
   Velocity saturation
   In semiconductors, when a strong enough electric field is applied, the carrier velocity in the semiconductor reaches a maximum value, saturation velocity. When this happens, the semiconductor is said to be in a state of velocity saturation...
   
   
4. impact ionization
   Impact ionization
   Impact ionization is the process in a material by which one energetic charge carrier can lose energy by the creation of other charge carriers...
   
   
5. hot electron effect