Abstract: This invention relates to memtransistors, fabricating methods and applications of the same. The memtransistor includes a polycrystalline monolayer film of an atomically thin material. The polycrystalline monolayer film is grown directly on a sapphire substrate and transferred onto an SiO2/Si substrate; and a gate electrode defined on the SiO2/Si substrate; and source and drain electrodes spatially-apart formed on the polycrystalline monolayer film to define a channel region in the polycrystalline monolayer film therebetween. The gate electrode is capacitively coupled with the channel region.