Semiconductor structure and forming method thereof

A method of forming a semiconductor structure, comprising:

• forming a stacked structure on a substrate, wherein the stacked structure comprises at least one first material layer and at least one second material layer that are stacked in a direction perpendicular to the substrate, and the at least one first material layer and the at least one second material layer are made of different materials;
• etching the stacked structure using a first etching gas to form a first opening that penetrates through the at least one second material layer, wherein the first etching gas comprises fluoride ions;
• introducing a first protective gas and a first auxiliary gas simultaneously into the first opening for reaction to form a protective layer on a sidewall of the first opening, wherein the first protective gas comprises silicon ions, and the first auxiliary gas comprises oxygen ions;
• etching the stacked structure using the first etching gas to form a second opening that penetrates through the at least one first material layer, wherein orthographic projections of the second opening and the first opening on the substrate at least partially overlap;
• and
• introducing the first protective gas and the first auxiliary gas simultaneously into the second opening for reaction to form a protective layer on a sidewall of the second opening.