Effects of Symmetric and Asymmetric Double-Layer Spacers on a Negative-Capacitance Nanosheet Field-Effect Transistor

The effect of three double-layer spacers (corner/selective/dual) on the performance of a negative-capacitance nanosheet field-effect transistor (NC-NSFET) was investigated for the first time. Sentaurus technology computer-aided design simulations revealed that the NC-NSFET with corner spacer will be significantly improved in transfer and high frequency characteristics due to the increase of ferroelectric layer thickness, and the NC-NSFET with a selective spacer structure exhibits better gate controllability. Compared with the ordinary dual- k spacer structure, the switching current ratio is doubled, and its subthreshold swing and drain-induced barrier lowering are reduced by 3.0% and 48%, respectively. In addition, by introducing a selective spacer at the source side and a corner spacer at the drain side, the NC-NSFET has a smaller intrinsic delay and exhibits better capacitance matching and stronger gate controllability than that with a symmetric spacer. For the double-layer spacer, the extension of the high- k spacer in the horizontal direction is more beneficial to the improvement of the device performance than that in the vertical direction, which provides a more comprehensive reference for the spacer application in NC-NSFET.