Semiconductor structure and forming method thereof

A forming method of a semiconductor structure, comprising:

• providing a base, comprising a device region and a zero mark region used for forming a zero mark trench, the device region comprises a first device subregion used for forming a first-type transistor and a second device subregion used for forming a second-type transistor;
• forming the zero mark trench inside the base in the zero mark region;
• after forming the zero mark trench, removing a partial thickness of the base in the first device subregion and the second device subregion to form a groove in the base and growing epitaxially a channel material layer in the zero mark trench and the groove;
• after forming the groove and growing the channel material layer, filling the zero mark trench, to form a dielectric layer located in the zero mark trench;
• forming a fin mask material layer covering the base and the dielectric layer;
• forming a mandrel layer on the fin mask material layer above the dielectric layer and the base in the device region, wherein the mandrel layer covers a top portion of the dielectric layer;
• forming a mask spacer on a side wall of the mandrel layer;
• removing the mandrel layer;
• etching the fin mask material layer using the mask spacer as a mask after the mandrel layer is removed, to form a fin mask layer;
• and
• etching a partial thickness of the base using the fin mask layer as a mask, wherein the remaining base after etching is used as a substrate, and a protrusion located on the substrate in the device region is used as a fin, and etching a partial thickness of the dielectric layer during the etching of the base.