Fig. 1. Concept of cointegrated single-transistor neurons and synapses.

(A) Schematic of biological neuron and synapse. About 10¹¹ neurons and 10¹⁵ synapses are densely interconnected in human brain. (B) Schematic of cointegrated single-transistor neurons and synapses. They have exactly the same SONOS structure, which includes a charge trap layer (Si₃N₄) in the gate dielectrics as shown in the cross-sectional transmission electron microscopy (TEM) image. They are fabricated with the same fabrications and connected through metallization. (C) Operation scheme of the neuron and synapse. The input and output of the neuron are current and voltage, respectively, while those of the synapse are voltage and current. (D) Fabricated 8-inch wafer in which single-transistor neurons, synapses, and additional CMOS circuits were cointegrated. It was fabricated with 100% standard Si CMOS fabrications. Photo Credit: J.-K. Han, Korea Advanced Institute of Science and Technology (KAIST).