For electronics, electronic semiconductor devices, a native transistor (or sometimes natural transistor) is a variety of the MOSFET, MOS field-effect transistor that is intermediate between MOSFET#Modes of operation, enhancement and depletion modes. Most common is the n-channel native transistor.
Historically, native transistors were referred to as MOSFETs without specially grown oxide, only natural thin oxide film formed over silicon during processing of other layers.
A native MOSFET is a transistor with nearly zero threshold voltage. Native n-channel transistors have a niche applications in low-voltage operational amplifiers and in low-voltage digital memory, where it functions as the weak pull-down. It is also used in low-voltage interface circuits. In most CMOS processes, native N-channel MOSFETs are fabricated on the "native" slightly Doping (semiconductor), p-doped silicon that comprises the bulk region, whereas a non-native N-channel MOSFET is fabricated in a p-well, which has a higher concentration of Electric charge, positive charges due to the increased presence of Electron hole, holes.
The lower concentration of positive charges in the channel of a native device means that less voltage at the gate terminal is required to repel these positive charges and form a depletion region under the gate with a conducting channel, which translates to the native device having a smaller threshold voltage.
The main disadvantages of the native transistor are the larger size due to additional doping mask, and sometimes lower transconductance. Native silicon has a lower conductivity than silicon in an n-well or p-well, as most MOSFETs are, and therefore must be larger to achieve equivalent conductance. Typical minimal size of the native N-channel MOSFET (NMOS) gate is 2-3 times longer and wider than standard threshold voltage transistor. The cost of chips including native transistors is also increased because of the additional doping operations.
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External links
Native NMOS circuit example
Transistor types
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