This is a very local effect within the FE material.

The QSNC is observed only at the domain boundaries. While recently the existence of steady-state NC (stabilized QSNC) was claimed again 13, nevertheless it doesn’t completely resolve the controversy. Until now there has been no scientific falsification of either of these approaches. In 10 authors have shown that all experimental observations can be explained both from a Landau model (assuming QSNC exists) as well as a Miller model (assuming QSNC does not exist). The steep-slope behavior observed in MOS devices is also explained from this concept 11, 12. The opposing school claims the phenomenon is attributed to a dynamic effect of the polarization switching that causes a snap-back in the voltage across the FE layer.

After the first direct demonstration of NC, there have been several papers giving alternative explanations for the experimental observations 8– 11. However, this is still a topic of scientific controversy. In addition, direct observation of NC was reported in 7 as well. Subsequently, sub 60mV/dec behavior in limited regions of the FE MOS subthreshold regime has been experimentally demonstrated as well as explained by QSNC theory in various works 2– 6. The theory predicted a surface potential amplification upon stabilization of the quasi-static NC, which is quantified by the body factor ‘ m’. This concept assumed that a quasi-static ( QS) NC can occur in FE based dielectric stacks, and a Landau based formalism was used to predict its existence 1.

The Negative Capacitance (NC) based FET in which the regular gate oxide would be replaced by a ferroelectric (FE) oxide was proposed some time ago to beat this “Boltzmann tyranny” 1. Breaking this limit has been the topic of intense investigations over the last years as it would allow producing CMOS circuits that consume less power. This leads to a fundamental limit in the steepness of the I-V characteristic in the subthreshold regime, which is 60mV/dec at room temperature. In the non-degenerate limit, the charge carriers in a MOSFET follow the Boltzmann distribution.

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