Semiconductor device having smooth refractory metal silicide layers and process for fabrication thereof

Abstract

A p-channel type field effect transistor incorporated in a semiconductor device has a gate electrode on a gate insulating layer, and the gate electrode is constituted by an amorphous silicon layer on the gate insulating layer, a silicon-germanium layer on the amorphous silicon layer, a polysilicon layer on the silicon germanium layer, a barrier layer of silicon oxide on the polysilicon layer residue of a cap silicon layer on the barrier layer and a cobalt silicide layer on the residue; while heat is being applied, boron, which has been ion implanted into the polysilicon layer and active region on both sides of the gate electrode, is activated with the assistance of germanium, and the barrier layer blocks the boundary between the cap silicon layer and the cobalt layer from the germanium so that the cobalt silicide forms a continuous layer without any coagulation.