Semiconductor structure and forming method thereof

The invention discloses a semiconductor structure and a forming method thereof, and the method comprises the steps: forming a first dielectric layer at the side wall of a word line at the junction of a storage unit region and an isolation region, the top of a protection layer, and the top of a gate insulation layer of the isolation region, and enabling the first dielectric layer to be filled in an opening of the isolation region; after the first dielectric layer is formed, the first dielectric layer in the storage unit region and the first dielectric layer located at the top of the gate insulating layer in the isolation region are removed, and the remaining first dielectric layer is located in the opening of the isolation region; removing the protection layer after removing the first dielectric layer in the storage unit region and the first dielectric layer located at the top of the gate insulation layer in the isolation region; and after the protection layer is removed, a barrier layer covering the word line