Semiconductor structure and forming method thereof

A method of forming a semiconductor structure, comprising:

• providing a base and a plurality of stack structures that are located on the base, arranged at intervals, and extend along a first direction, wherein the stack structures each comprise a plurality of semiconductor layers arranged at intervals in a direction perpendicular to a surface of the base, and a top surface and a bottom surface opposite to each other of each of the semiconductor layers are each provided with a first sacrificial layer, a surface of the first sacrificial layer that is away from the semiconductor layer is provided with a second sacrificial layer, a same etching process has different etching rates for the first sacrificial layer and the second sacrificial layer, an isolation layer is provided between adjacent ones of the stack structures, and the base comprises a word line region;
• removing a part of the isolation layer in the word line region, to expose a sidewall of a part of each of the first sacrificial layers in the word line region and a sidewall of a part of each of the second sacrificial layers in the word line region;
• removing the part of each of the first sacrificial layers in the word line region;
• forming an initial word line layer in the word line region, wherein a region between the part of each of the second sacrificial layers and a part of a corresponding semiconductor layer, and a region between adjacent ones of parts of the semiconductor layers are filled with the initial word line layer;
• removing the part of each of the second sacrificial layers in the word line region, to form an etching hole;
• and
• partially removing the initial word line layer exposed by the etching hole, to form a plurality of word line structures that are arranged at intervals along the direction perpendicular to the surface of the base.