2. Thin-film CMOS technologies

From the 28/20 nm technology nodes onwards, the technology used to manufacture CMOS chips has shifted from bulk to thin-film silicon technologies. In fact, these are the only technologies used today in advanced technology nodes. The reason is simple: with the scaling of transistor geometrical dimensions from one technology node to the next, and the end of Dennard's scaling law in 2003, it became increasingly difficult to ensure electrostatic control of the MOS transistor channel. The transistors' electrical characteristics were deteriorating, particularly leakage currents, due to leakage deep into the silicon substrate, uncontrolled by the gate. The specifications in terms of the ratio I _ON /I _OFF could no longer be met: this ratio is important because the numerator, which is the current delivered...