  We present quantum simulations of carbon nanotube field-effect transistors
(CNT-FETs) based on top-gated architectures and compare to electrical
characterization on devices with 15 nm channel lengths. A non-equilibrium
Green's function (NEGF) quantum transport method coupled with a $\vec{k} \cdot
\vec{p}$ description of the electronic structure is demonstrated to achieve
excellent agreement with the reported experimental data. Factors influencing
the electrostatic control of the channel are investigated and reveal that
detailed modeling of the electrostatics and the electronic band structure of
the CNT is required to achieve quantitative agreement with experiment.
