Geometrical and Structural Design Schemes for Trench-Shaped Vertical Channel Transistors Using Atomic-Layer Deposited In-Ga-Zn-O

Trench-structured In-Ga-Zn-O vertical thin-film transistors (T-VTFT) was fabricated with a channel length of 400 nm. T-VTFTs showed channel width-dependent field-effect mobility owing to the back-channel scattering, and the mobility of 24.1 cm2
$/$
Vs was finally obtained with a channel width of
$1 ~\mu \text{m}$
. Alternatively, the asymmetric operations of conventional mesa-shaped VTFTs were improved in a symmetrical way owing to the structural benefits of the T-VTFT, leading to excellent immunity against the drain-induced barrier lowering.