A STRUCTURE OF LDD IN MULTI-DEVICES AND A FABRICATION METHOD THEREOF

摘要

An LDD(Lightly Doped Drain) structure of a MOS(Metal Oxide Silicon) transistor inside multi devices and a forming method thereof are provided to omit a mask for an ion implantation process by using thickness difference of a gate oxide layer and the difference of the LDD ion implantation energy. A first gate oxide layer(202) and a second gate oxide layer(203) are formed in a front side of a wafer. The second gate oxide layer is thicker than the first gate oxide as much as a predetermined step(204). A fist ion implantation process is performed for forming the LDD of a first MOS transistor. The implanted ion is included in the depth corresponding to the step from the upper part of the second gate oxide layer. A second ion implantation process is performed for forming the LDD of a second MOS transistor. The step is removed.