A semiconductor device with stress trench isolation and a method for forming the same are provided. The method includes: providing a silicon substrate; forming first trenches and second trenches on the silicon substrate, wherein an extension direction of the first trenches is perpendicular to that of the second trenches; forming a first dielectric layer in the first trenches and forming a second dielectric layer in the second trenches; and forming a gate stack on a portion of the silicon substrate surrounded by the first trenches and the second trenches, wherein a channel length direction under the gate stack is parallel to the extension direction of the first trenches, indices of crystal plane of the silicon substrate are {100}, and the extension direction of the first trenches is along the crystal orientation . The embodiments of the present invention can improve response speed and performance of the devices.