SOI transistors with improved source/drain structures with enhanced strain

摘要

A transistor structure with improved device performance, and a method for forming the same is provided. The transistor structure is an SOI (silicon-on-insulator) transistor. In one embodiment, a silicon layer over the oxide layer is a relatively uniform film and in another embodiment, the silicon layer over the oxide layer is a silicon fin. The transistor devices include source/drain structures formed of a strain material that extends through the silicon layer, through the oxide layer and into the underlying substrate which may be silicon. The source/drain structures also include portions that extend above the upper surface of the silicon layer thereby providing an increased volume of the strain layer to provide added carrier mobility and higher performance.

主权项

1. A semiconductor device comprising:
a substructure including a substrate that is silicon, a buried oxide layer formed over said silicon substrate and a crystalline silicon material formed over said buried oxide layer, the substructure including openings extending from a top surface of the crystalline silicon material through the buried oxide layer and into the substrate; a plurality of gate structures formed over said crystalline silicon material, a gate structure of the plurality of gate structures having a pair of sidewall spacers with a gate electrode therebetween; source/drain structures disposed adjacent said gate electrode, said source/drain structures comprising a strain material that is a different material than said silicon substrate, the strain material filling the openings, the strain material having an upper portion extending above said crystalline silicon material; and graded dopant impurity regions in said silicon substrate entirely below the strain material in a region entirely between sidewall spacers of two adjacent gate structures of the plurality of gate structures, the graded dopant impurity regions formed of silicon doped with impurities, the graded dopant impurity regions located beneath respective bottom surfaces of said strain material.