Semiconductor device including reflow layers

Abstract

A semiconductor device includes a substrate that includes an active pattern, a channel pattern disposed on the active pattern, where the channel pattern includes a plurality of semiconductor patterns that are vertically stacked and spaced apart from each other, a source/drain pattern connected to the semiconductor patterns, and a gate electrode disposed on the semiconductor patterns. The gate electrode includes a plurality of portions that are respectively interposed between the semiconductor patterns, and the source/drain pattern includes a buffer layer in contact with the semiconductor patterns and a main layer disposed on the buffer layer. The buffer layer contains silicon germanium (SiGe) and includes a first semiconductor layer and a first reflow layer thereon. A germanium concentration of the first reflow layer is less than that of the first semiconductor layer.