Fabrication process for MOSFET using oblique rotation ion implantation

DETAILED DESCRIPTION It is an object of the present invention to provide a fabrication process of a short-channel MOSFET, which can reduce fluctuation of ON current relative to fluctuation of a width of a side wall spacer formed on the side surface of the gate electrode and formed with an insulation layer.
A fabrication process of a MOSFET according to the present invention, comprises the steps of: forming a gate oxide layer on a device forming region of a major surface of a silicon substrate having at least an impurity region of one conductive type; forming a gate electrode on the surface of the gate oxide layer; forming a side wall spacer made of an insulation layer, on a side surface of the gate electrode; performing oblique rotation ion implantation of one conductive type impurity with taking the gate electrode and the side wall spacer as mask to form an ion implanted layer of one conductive type at a first depth position from the surface of said impurity region of one conductive type; performing ion implantation of the other conductive type impurity on the surface of the substrate with taking the gate electrode and the side wall spacer as mask, in a direction perpendicular to said substrate to form an ion implanted layer of other conductive type at a second depth position from the surface of said impurity region of one conductive type, the second depth position being deeper than the first depth position; and activating said ion implanted layer of one conductive type and said ion implanted layer of the other conductive type by heat treatment.
In the present invention, after formation of the side wall spacer on the side surface of the gate electrode, the impurity of one conductive type is implanted by way of oblique rotation ion implantation with taking the gate electrode and the side wall spacer as a mask, and subsequently the impurity of the other conductive type is implanted by perpendicular ion implantation.
Therefore, it is possible to avoid lowering of concentration of the other conductive type impurity to that less than the concentration of the channel region at the end portion of the gate electrode by one conductive type impurity and the other conductive type impurity are both affected by the width of the side wall spacer