For sustainable advancements in electronics technology, the field of neuromorphic electronics, i.e., electronics that imitate the principle behind biological synapses with a high degree of parallelism, has recently emerged as a promising candidate for novel computing technologies. Toward realizing a massively parallel neuromorphic system, it is essentially required to develop an artificial synapse capable of emulating various synaptic functionality, such as short- and long-term synaptic plasticity with ultralow power consumption and robust controllability. In this talk, as a first part, I will present the general introduction of neuromorphic hardware technology based on the research background and synaptic device requirements for artificial neural networks. As a second part, I will briefly introduce our recent approaches and achievements for artificial syanpses using diverse functional nanomaterials on advanced device architectures.