Field-effect transistors (fets) employing thermal expansion of work function metal layers for strain effect and related fabrication methods

Abstract

Forces applied to the channel regions of semiconductor slabs in a first direction relative to the semiconductor slab, can create strains in the crystal structure that improve carrier mobility to improve drive strength in the channel region. In a three-dimensional (3D) FET structure, a work function metal layer is provided on opposing faces of semiconductor slabs to cause a force to be exerted on the channel regions in a first direction corresponding to current flow. The force in the first direction is either tensile force or compressive force, depending on a FET type (N or P) employing the semiconductor slab, and is provided to create strain in a crystalline structure of the semiconductor slab to improve carrier mobility in the channel region. Increasing carrier mobility in the channel regions in a 3D FET structure increases drive strength of the 3D FET, which saves area in an integrated circuit.