A method is provided for fabricating transistors. The method includes providing a semiconductor substrate. The substrate has a gate film and a mask film formed on a top surface. The mask film contains implanted carbon ions. The method further includes forming a mask layer by etching the mask film and then forming a gate layer by etching through the gate film using the mask layer as a mask until the substrate is exposed. The method also includes forming a first sidewall containing implanted carbon ions on the side surface of the gate layer and the mask layer; forming a stress layer in the substrate on both sides of the gate layer and the first sidewall; and forming a source region on one side of the gate layer and the first sidewall and a drain region on the other side of the gate layer and the first side wall.