Semiconductor device having nanosheet transistor and methods of fabrication thereof

Abstract

Embodiments provide a method for forming a semiconductor device structure, includes forming a fin structure having first semiconductor layers and second semiconductor layers alternatingly stacked thereover, forming a sacrificial gate structure over a portion of the fin structure, removing portions of the sacrificial gate structure to expose the first and second semiconductor layers, removing portions of the second semiconductor layers to expose portions of each of the first semiconductor layers. The method includes surrounding the exposed portions of each of the first semiconductor layers with a cladding layer, wherein the cladding layer is formed of a material chemically different from the first semiconductor layers, and the cladding layer has a first atomic percentage of germanium. The method includes performing a thermal treatment so that germanium atoms of the cladding layer are diffused into and reacted with the first semiconductor layer to form an intermixed layer, wherein the intermixed layer has a second atomic percentage of germanium that is less than the first atomic percentage of germanium. The method includes forming a gate electrode layer to surround each of the intermixed layers.