2. From planar MOSFET to multi-gate and 3D architectures

In thin and/or lightly doped silicon films, the simultaneous activation of the front and back channels by 2, 3 or 4 gates induces the phenomenon of volume inversion. Unknown in bulk silicon MOS devices, this effect allows the inversion charge to cover the entire silicon film, giving rise not only fully depleted, but also fully inverted devices. The resolution of the Poisson and Schrödinger equations indicates that the maximum density of the inversion charge is obtained at the center of the film. This causes increases in transconductance and drain current in the ON state, a decrease in the influence of interface defects (traps, fixed charges, roughness) and low frequency 1/ f noise. A low subthreshold slope close to 60 mV/decade down to sub-deca-nanometric gates is possible with this type of transistor architecture. Multiple-gate MOSFETs (double gate...