Inversion-sensing SiO2-based MOS capacitive synapse for neuromorphic computing

Abstract

In this work, an inversion-sensing SiO2-based capacitive synapse device was introduced by using the lateral coupling effect in a concentric metal–oxide–semiconductor structure. The device achieved a CHCS/CLCS ratio of 24 with a low programming voltage of VPGM = −2.5 V. Technology Computer Aided Design (TCAD) simulations confirmed the device's high sensitivity to changes in external charges. For oxide with an effective positive charge density (Neff) exceeding 2.8×1011 cm−2, a small variation of 5×109 cm−2 could influence a lot in the capacitance value of the device in the inversion region. This sensitivity enabled multi-state capacitance modulation by adjusting the number of pulses and operating voltages. Additionally, the scalability of the device was validated through simulations. The on/off ratio could be further improved by substituting the gate dielectric material. Overall, the lateral coupling effect not only enhances the performance of charge-trapping-based devices but also provides a viable strategy for expanding memory windows across various types of capacitive memory technologies.