Graded-junction gate/n super(-) overlapped LDD MOSFET structures for high hot-carrier reliability

A newly developed gate/n super(-) overlapped LDD MOSFET has been investigated. The MOSFET was fabricated by an oblique rotating ion implantation technique. A new formula of impurity ion profile was derived to analyze the lowering of substrate current and improvement of the degradation caused by hot-carrier effect. It was proved that impurity ion profile near the drain edge is remarkably graded in the direction both along channel and toward substrate even just after the implantation, so that maximum lateral electric field is remarkably relaxed as compared with conventional LDD MOSFET.