**7. Summary and conclusions**

A review of recent results obtained on 28 nm FDSOI transistors operated down to deep cryogenic temperatures has been presented. First, the main device electrical properties in terms of gate capacitance and charge control and drain current transfer characteristics have been discussed along with the temperature dependence of the major MOSFET parameters (threshold voltage, subthreshold swing and mobility). Then, the self-heating phenomena were characterized in details, providing valuable information about the actual device temperature versus power dissipation, as well as the thermal resistance that limits the heat dissipation in the FDSOI structure, especially at low temperature. The matching properties have then been studied owing to threshold voltage and drain current statistical variability analysis, revealing that the mismatch in FDSOI transistors only increases of about 30–40% at deep-cryogenic temperatures. Besides, Poisson-Schrodinger simulations have been carried out with success down to zero Kelvin, giving access to valuable information about the gate charge control in FDSOI structures versus temperature, and, providing physical insight to the development of compact model mandatory for FDSOI circuit design at deep cryogenic temperatures. Finally, the operation of elementary circuits such as ring oscillators and voltage controlled oscillators has been demonstrated in terms of inverter delay and clock frequency down to deep-cryogenic temperatures.

This work highlights the powerful advantage of FDSOI over bulk technology, led by the back biasing capability. It offers in particular an efficient way to manage power consumption and performance, thus mitigating thermal effects, which are crucial aspects in cryo-electronics.
