rapid thermal anneal causes driving in of the n dopant implant the result of this is that even if some of the silicon of the n region 40 is consumed by the tungsten during tungsten deposition nevertheless the n implant is sufficiently deep so as not substantially to be affected by the tungsten thereby affecting the subsequent operation of the source drain regions typically the junction depth is about 0 25 u03bcm whereas about 0 1 u03bcm of silicon is removed by the tungsten deposition the implant ensures sufficient resultant junction depth for the operation of the device not to be jeopardized by the removal of an upper part of the silicon during tungsten deposition similarly for the p dopant i e boron implant this also provides a deeper p region 42 which is enhanced by the rapid thermal anneal which drives the p dopant deeper into the silicon substrate in addition this also gives a higher p concentration at the interface with the tungsten which results in an improved electrical contact between the tungsten and the p region which consequently lowers the contact resistance of the p sources and drains the rapid thermal anneal actuates the implant without causing diffusion of the implant this removes defects in the silicon lattice the rapid thermal anneal also smooths out the rpsg interlevel dielectric layer which leads to improved tungsten deposition since the u201c window.