Semiconductor device and preparation method thereof

The invention provides a semiconductor device and a preparation method thereof, and the semiconductor device comprises a substrate, a first electric connecting piece, a second electric connecting piece, a grid electrode, a grid dielectric layer, a channel layer, an isolation structure and a metal structure layer, the first electric connecting pieces and the second electric connecting pieces are alternately arranged in the first insulating structure layer along a first direction; the grid electrode is located on the first electric connecting piece, and the bottom surface of the grid electrode is contacted with the top surface of the first electric connecting piece; the gate dielectric layer covers the gate, and the channel layer covers the gate dielectric layer; the isolation structures are located on the two sides of the channel layer, and the top surfaces of the isolation structures are lower than the top surface of the channel layer; the metal structure layer covers the adjacent second electrical connectors