A structure and an operation of a transistor, which is a vertical transistor in which a nanowire-type floating body layer is vertically formed or a horizontal transistor in which a floating body layer is horizontally formed, and implements a spike operation of a neuron by storing and releasing charges inside the transistor, and a neuromorphic system using the same are provided. The vertical transistor includes a floating body layer in a form of a vertical nanowire vertically formed on a substrate, a source and a drain formed above and below the floating body layer, a gate insulating layer formed on the source and surrounding the floating body layer, a gate formed outside the gate insulating layer, and a contact metal being in contact with the source, the drain and the gate to input or output an electrical signal.