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By the end of the first half of the 1950s, following theoretical and experimental work of Bardeen, Brattain, Kingston, Morrison and others, it became more clear that there were two types of surface states. Fast surface states were found to be associated with the bulk and a semiconductor/oxide interface. Slow surface states were found to be associated with the oxide layer because of [[adsorption]] of atoms, molecules and ions by the oxide from the ambient. The latter were found to be much more numerous and to have much longer [[relaxation (physics)|relaxation time]]s. At the time [[Philo Farnsworth]] and others came up with various methods of producing atomically clean semiconductor surfaces.
In 1955, [[Carl Frosch]] and Lincoln Derrick accidentally covered the surface of silicon [[wafer (electronics)|wafer]] with a layer of [[silicon dioxide]]. They showed that oxide layer prevented certain dopants into the silicon wafer, while allowing for others, thus discovering the [[Passivation (chemistry)|passivating]] effect of [[Thermal oxidation|oxidation]] on the semiconductor surface. Their further work demonstrated how to etch small openings in the oxide layer to diffuse dopants into selected areas of the silicon wafer. In 1957, they published a research paper and patented their technique summarizing their work. The technique they developed is known as oxide diffusion masking, which would later be used in the [[semiconductor device fabrication|fabrication]] of MOSFET devices.<ref name=":1">{{Cite journal |last=Frosch |first=C. J. |last2=Derick |first2=L |date=1957 |title=Surface Protection and Selective Masking during Diffusion in Silicon |url=https://iopscience.iop.org/article/10.1149/1.2428650 |journal=Journal of The Electrochemical Society |language=en |volume=104 |issue=9 |pages=547 |doi=10.1149/1.2428650}}</ref> At Bell Labs, the importance of Frosch's technique was immediately realized. Results of their work circulated around Bell Labs in the form of BTL memos before being published in 1957. At [[Shockley Semiconductor Laboratory|Shockley Semiconductor]], Shockley had circulated the preprint of their article in December 1956 to all his senior staff, including [[Jean Hoerni]].<ref name="Moskowitz" /><ref>{{cite book |author1=Christophe Lécuyer |author2=David C. Brook |author3=Jay Last | title=Makers of the Microchip: A Documentary History of Fairchild Semiconductor | date=2010 | pages=62–63 |publisher=MIT Press | isbn=978-0-262-01424-3 | url=https://books.google.com/books?id=LaZpUpkG70QC&pg=PA62}}</ref><ref>{{cite book |last1=Claeys |first1=Cor L. |title=ULSI Process Integration III: Proceedings of the International Symposium |date=2003 |publisher=[[The Electrochemical Society]] |isbn=978-1-56677-376-8 |pages=27–30 | url=https://books.google.com/books?id=bu22JNYbE5MC&pg=PA27}}</ref>
In 1955, [[Ian Munro Ross]] filed a patent for a [[FeFET]] or MFSFET. Its structure was like that of a modern inversion channel MOSFET, but ferroelectric material was used as a dielectric/insulator instead of oxide. He envisioned it as a form of memory, years before the [[floating gate MOSFET]]. In February 1957, [[J. Torkel Wallmark|John Wallmark]] filed a patent for [[thin-film transistor|FET]] in which [[germanium monoxide]] was used as a gate dielectric, but he didn't pursue the idea. In his other patent filed the same year he described a [[multigate device|double gate]] FET. In March 1957, in his laboratory notebook, Ernesto Labate, a research scientist at [[Bell Labs]], conceived of a device similar to the later proposed MOSFET, although Labate's device didn't explicitly use [[silicon dioxide]] as an insulator.<ref>{{cite book |last1=Lojek |first1=Bo |title=History of Semiconductor Engineering |date=2007 |publisher=Springer Science & Business Media |isbn=978-3-540-34258-8 |page=324}}</ref><ref>{{cite book | author=Stefan Ferdinand Müller | title=Development of HfO2-Based Ferroelectric Memories for Future CMOS Technology Nodes | year=2016 | isbn=978-3-7392-4894-3}}</ref><ref>{{cite book |author1=B.G Lowe |author2=R.A. Sareen | title=Semiconductor X-Ray Detectors | date=2013 |publisher=CRC Press | isbn=978-1-4665-5401-6 }}</ref><ref name="Bassett22">{{cite book |last1=Bassett |first1=Ross Knox |title=To the Digital Age: Research Labs, Start-up Companies, and the Rise of MOS Technology |date=2007 |publisher=Johns Hopkins University Press |isbn=978-0-8018-8639-3 |page=22 |url=https://books.google.com/books?id=UUbB3d2UnaAC&pg=PA22}}</ref>
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