His achievements are great, but the only reason why he could this without a cleanroom and with less pure chemicals is that he succeeded to find on eBay a batch of silicon wafers with the MOS gate oxide already grown on them.

Growing the MOS gate oxide without extreme cleanness has no chance of succeeding.

The difficulty of this process has caused a delay of many decades between the time when the MOS transistor was first imagined (in 1928 by Julius Edgar Lilienfeld, then also in 1935 by Oskar Heil) and the time when working MOS transistors were made for the first time, around 1960.