Transistor and method of forming same

The disclosure provides for a transistor which may include: a gate stack on a substrate, the gate stack including a gate dielectric and a gate electrode over the gate dielectric; a channel within the substrate and under the gate stack; a doped source and a doped drain on opposing sides of the channel, the doped source and the doped drain each including a dopant, wherein the dopant and the channel together have a first coefficient of diffusion and the doped source and the doped drain each have a second coefficient of diffusion; and a doped extension layer separating each of the doped source and the doped drain from the channel, the doped extension layer having a third coefficient of diffusion, wherein the third coefficient of diffusion is greater than the first coefficient of diffusion and the second coefficient of diffusion is less than the third coefficient of diffusion.