Re: silicon dioxide in mosfets for gate insulation
Why SiO2 became so popular:
- ease of growth (oxidation of Si)
- very high quality of oxide (good for low leakage, high reliability, etc.)
- very high quality of Si-SiO2 interface (low defect density) - important for carrier transport in inversion layer
But starting from ~90nm technology, nitrogen was added to SiO2 (nitridation - using various processes), to prevent boron penetration from the doped gate (or pMOSFETs) to the channel, and to somewhat increase the dielectric constant.
Then, high-K dielectrics (usually on top of a very thin SiO2 - for interface quality purpose) were introduced, to increase physical thickness and to reduce tunneling thropugh gate dielectric.