Complementary metal oxide semiconductor device and method of forming the same

A method for forming a complementary metal oxide semiconductor device, comprising:

• forming a deep trench in a substrate to define a first fin structure and a second fin structure in the substrate;
• forming a first trench cutting through the first fin structure and forming a first material filling the deep trench and the first trench;
• forming a second trench cutting through the second fin structure and forming a second material filling the second trench, wherein the first material and the second material comprise different stresses;
• and
• forming a first gate structure and a second gate structure disposed atop the first material and the second material respectively, wherein the first gate structure completely covers the first trench and the second gate structure completely covers the second trench.