Abstract: A field effect transistor having metallic silicide layers is formed in a semiconductor layer on an insulating layer of an SOI substrate. The metallic silicide layers are composed of refractory metal and silicon. The metallic silicide layers extend to bottom surfaces of a source and a drain regions. A ratio of the metal to the silicon in the metallic silicide layers is X to Y. A ratio of the metal to the silicon of metallic silicide having the lowest resistance among stoichiometaric metallic silicides is X0 to Y0. X, Y, X0 and Y0 satisfy the following inequity: (X/Y)>(X0/Y0).

Abstract: A protective layer is formed on a metallic silicide layer prior to a heat treatment for reducing a resistance of the metallic silicide layer. As a result, vertical growing of crystallization in the metallic silicide layer is restrained by the protective layer during the heat treatment. Moreover, the crystallization in the metallic silicide layer easily grows along the protective layer. Therefore, evenness of the metallic silicide layer can be maintained.