Process for manufacturing a single asymmetric pocket implant
 A process is described for forming a buried, or pocket, ion implant in a semiconductor device. In particular, said pocket is limited to only the drain side of a field effect transistor. To achieve this the photoresist that is used to protect the source and drain regions during ion implantation is located at different distances from the gate pedestal. The photoresist on the source side is placed closer to the gate pedestal than it is on the drain side. As a result, when ions arrive at the surface at a sufficiently shallow angle to be able to penetrate the semiconductor regions immediately beneath the gate oxide, photoresist at the source side blocks the beam while the photoresist on the drain side is far enough away from the gate not to intercept the beam. Thus, a single asymmetrically located pocket is formed in a single step. 
Taiwan Semiconductor Manufacturing Company
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Chaochieh Jing-Meng Jau-Jey
Tsai Liu Wang