[SOLVED] why name Metal-Oxide-Semiconductor (MOSFET) even poly-Si is used?

[praveen_k]

Hi,

Even poly-Si replaced metal as gate in MOSFETs, why the nomenclature as Metal-Oxide-Semiconductor (MOSFET) still exists? Its now Poly-Oxide-Semiconductor. Already there's POSFET for touch sensing devices, may be this can be changed to something else. Right?

Or is there any specific reason for why they still call it as MOSFET only?

 

[FvM]

Poly-Si acts as conductor, there's no difference in terms of device operation principles.

 

[dick_freebird]

Because at this point changing every bit of documentation
ever written for a trivial distinction has value less than zero?

 

[timof]

Just to add to earlier comments -

It's an interesting question.

One of the main attributes of the gate is low resistivity (or high conductivity), so, theoretically, the ideal name for the structure would be conductor - oxide - semiconductor. But, in early days, metals were used as a gate material - that's why the name - MOS (metal - oxide - semiconductor), and it stayed this way, at least for historical reasons.

"Poly", on the other hand, has many different "options" (so to speak) - low-resistivity, high-resistivity, silicided, non-silicided, etc. - so, a term "poly" itself is not associated with low resistance, required for gate material.

By the way, in recent technologies, companies returned to using metal gates, instead of polysilicon gates (mainly to avoid polysilicon depletion effect).

Term "oxide" is equally rather conventional - as other dielectrics can be used instead of silicon dioxide, and, in recent technologies, complex dielectric stacks, with combinations of different materials, are being used.

 

[schmitt trigger]

People get used to certain things, and the custom persists even after it has outlived its usefulness.

For instance, in most MS Windows software, the save icon is a floppy disk, even though floppies haven't been used in years.