  Ion-Sensitive Field-Effect Transistors (ISFETs) form a wide-spread technology
for sensing, thanks to their label-free detection and intrinsic CMOS
compatibility. Their current sensitivity, {\Delta}ID/ID, for a given
{\Delta}pH, however, is limited by the thermionic limit for the Subthreshold
Slope (SS) of Metal-Oxide-Semiconductor Field-Effect Transistors(MOSFET) and by
the Nernst limit. Obtaining ISFETs with a steep slope transfer characteristics
is extremely challenging. In this paper we combine the merits of traditional
ISFETs with the performance boosts offered by the insertion of a Negative
Capacitor in series with the Gate contact. In the proposed tests with NC PZT
capacitors, we demonstrate experimentally a reduction of the SS by 44%,
combined with a current efficiency improvement of more than two times. As a
consequence of the steeper SS, the current sensitivity to pH is improved by
78%.
