This paper presents an in-depth DC characterization of a 22 nm FDSOI CMOS technology down to deep cryogenic temperature, i.e., 2.95 K. The impact of the back-gate voltage (V-back) on device performance, i.e., threshold voltage (V-T) and carrier transport, is investigated over a wide temperature range. Moreover, semiclassical and quantum transports of two-dimensional carrier gas are investigated. The effective mobility (mu(eff)) extracted from short devices at cryogenic temperatures is lower than actual mobility due to the presence of ballistic transport. The discontinuous I-D-V-G is found in both long and extremely short transistors, which is ascribed to the intersubband transition happening during the scattering event. Oscillatory I-D-V-G due to resonant tunneling manifests itself in short devices at cryogenic temperatures and depends on V-back. On the other hand, the worse subthreshold swing is found for short devices in the saturation regime and at cryogenic temperatures due to source-to-drain tunneling.