Semiconductor device and formation method thereof

A method of forming a semiconductor device, comprising:

• providing a substrate;
• forming a plurality of first-type fin groups and second-type fins each between the first-type fin groups, on the substrate, wherein a first-type fin group includes first-type fins, and the first-type fins and the second-type fins are arranged in a direction perpendicular to an extending direction of the first-type fins and the second-type fins;
• removing the second-type fins to form first trenches between corresponding first-type fin groups;
• forming a protective layer on sidewalls of the first trenches after removing the second-type fins, wherein the protective layer covers sidewalls of the first-type fins that are perpendicular direction of the first-type fins;
• forming second trenches in the substrate under the first trenches by etching the substrate at bottoms of the first trenches using the protective layer as an etch mask;
• after forming the first trenches and before forming the second trenches, cutting out a portion of a first-type fin along the extending direction of the first-type fin to form a cutting groove in the first-type fin, and bottom areas of the cutting groove expose the substrate;
• and
• when forming the second trenches, etching the substrate at a bottom of the cutting groove to form third trenches in the substrate under the cutting groove.

A semiconductor device, comprising:

• a substrate;
• a plurality of first fin groups on the substrate;
• a plurality of second fin groups between adjacent first fin groups of plurality of first fin groups on the substrate, wherein each first fin group includes first fins, each second fin group includes second fins, each first fin has a cutting groove to separate the each first fin to two portions;
• a distance between adjacent second fins is greater than a distance between adjacent first fins, and the first fins and the second fins are arranged in a direction perpendicular to an extending direction of the first fins and the second fins;
• a protective layer on sidewalls of the first fins and the second fins filling up an opening between adjacent first fins;
• first trenches between each first fin group and an adjacent second fin group fins in the substrate;
• and
• second trenches between adjacent second fins in the substrate under the first trenches, wherein the first trenches, the second trenches, and the cutting groove have a same depth.