Semiconductor device and fabrication method thereof

A semiconductor device fabrication method comprising:

• providing a processing wafer, the processing wafer including a plurality of semiconductor mesas at least partially surrounded by a dielectric layer;
• performing a first etching to remove a portion of the dielectric layer in a first region to form a first recess having a first initial depth, a first mesa of the plurality of semiconductor mesas being in the first region;
• performing a second etching to remove a portion of the dielectric layer in a second region to form a second recess having a second initial depth different from the first initial depth, a second mesa of the plurality of semiconductor mesas being in the second region;
• and
• performing a third etching to deepen the first recess and the second recess until a vertical distance from a top of the first mesa to a bottom of the first recess reaches a first height and a vertical distance from a top of the second mesa to a bottom of the second recess reaches a second height different from the first height.

A semiconductor device comprising:

• a dielectric layer;
• a first recess and a second recess formed in the dielectric layer;
• a first FinFET formed in the first recess, the first FinFET including a first fin;
• and
• a second FinFET formed in the second recess, the second FinFET including a second fin;
• wherein a first recess depth measured from a top of the first fin to a bottom of the first recess is different from a second recess depth measured from a top of the second fin to a bottom of the second recess.