Why first NMOS device was fabricatd nearly a decade after PMOS fabrication?

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amit.31

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Hi all

What took so long that first NMOS device was fabricated after nearly a decade of PMOS fabrication?
Since it just need to reverse the source and substrate region.
 

Your assumptions are incorrect and do not reflect the complexity of process fabrication steps. THe initial fab processes did not work with n-ch depletion mode very well. They could only make p-ch dep. mode then when enhancement mode was possible, as I recall by replacing diffusion & thermal oxidation with ion implant and CVD deposition.


This shows some history.

**broken link removed**
 
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