Semiconductor devices and methods of manufacturing thereof

A method of fabricating a semiconductor device, comprising:

• forming a plurality of semiconductor fins in a first region on a substrate;
• forming an isolation region around the plurality of semiconductor fins, a top surface of the plurality of semiconductor fins being above a top surface of the isolation region;
• performing a first etch using a first etchant to etch the plurality of semiconductor fins such that a top surface of the plurality of semiconductor fins has a same height as a top surface of the isolation region;
• performing a second etch using a second etchant, different from the first etchant, to etch the isolation region to form a first recess in the isolation region laterally adjacent the semiconductor fins;
• and
• performing a third etch using a third etchant, different from the second etchant, to etch the plurality of semiconductor fins to remove the plurality of semiconductor fins and etch a second recess through the isolation region into the semiconductor substrate.

A semiconductor device, comprising:

• a semiconductor substrate;
• an isolation region disposed on the semiconductor substrate;
• a plurality of dummy fins in a first region extending from the isolation region;
• and
• a dielectric material extending through the isolation region and into the semiconductor substrate, the dielectric material disposed between the plurality of dummy fins;
• a height of the isolation region on an inner side of the plurality of dummy fins being less than a height of the isolation region on an outer side of the plurality of dummy fins.