1. A semiconductor device with a STAR structure, comprising: one or more stacked semiconductor layers spaced vertically apart from a substrate by a predetermined distance; a gate electrode formed to pass by all of the semiconductor layers and interlaid with a gate insulator on each of the semiconductor layers; source/drain regions formed at both sides of the gate electrode in each of the semiconductor layers; and an interlayer insulator wrapping around the source/drain regions of each of the semiconductor layers or filling a space between the semiconductor layers.