Effects of scalability and floating metal on NC-FETs based on a real-space atomic model

The influence of gate length and an internal floating metal layer on the performance of a negative capacitance (NC) field-effect transistor (FET) is investigated at an atomic level for the first time. Full three-dimensional (3D) polarization information is integrated in the Poisson solver in order to obtain a real-space potential profile of the NC-FET to understand the device performance. The body factor, dV G/dΨS, is studied to reflect the influence of the ferroelectric (FE) layer. For the same FE thickness, an increase in gate length results in a larger body factor and lower tunneling current. This tradeoff prevents the steady decrease of the subthreshold swing (SS). The effect of the floating metal layer between the FE and SiO2 layers for NC-FETs with different gate lengths is studied with detailed potential contours. The metal layer can influence the potential and conduction band (E C) profile of the NC-FET, especially with a longer channel. This results in a reduction in the SS and ON-state current. Beyond the previous work, these new findings provide further physical insight into the device characteristics and are instructive in ultra-scaled NC-FET designs.