P-type field effect transistor (pfet) on a silicon germanium (ge) buffer layer to increase ge in the pfet source and drain to increase compression of the pfet channel and method of fabrication

Abstract

An exemplary high performance P-type field-effect transistor (PFET) fabricated on a silicon (Si) germanium (Ge)(SiGe) buffer layer with a SiGe source and drain having a Ge percentage higher than a threshold that causes dislocations at a Si substrate interface is disclosed. A source and drain including a Ge percentage above a 45% threshold provide increased compressive strain in the channel for higher performance of the PFET. Dislocations are avoided in the lattices of the source and drain by forming the PFET on a SiGe buffer layer rather than directly on a Si substrate and the SiGe buffer layer has a percentage of Ge less than a percentage of Ge in the source and drain. In one example, a lattice of the buffer layer is relaxed by implanting dislocations at an interface of the buffer layer and the Si substrate and annealing the buffer layer.