The present disclosure relates to the technical field of semiconductors, and provides a memory device, and a semiconductor structure and a forming method thereof. The forming method includes: providing a substrate, where the substrate includes a source region and a drain region spaced apart from each other, and a gate trench located between the source region and the drain region; forming, in sequence on an inner wall of the gate trench, a gate oxide layer, an interface layer, and a conductive layer that fills the gate trench; and etching back the side of the interface layer away from the bottom of the gate trench by using a wet etching process, such that a top height of the interface layer is lower than a top height of the conductive layer.