Semiconductor devices

Abstract

A semiconductor device includes an active region, a plurality of channel layers disposed to be spaced apart from each other in a vertical direction on the active region, a gate structure extending in a second direction to intersect the active region and the plurality of channel layers and surrounding the plurality of channel layers, a source/drain region disposed on the active region on at least one side of the gate structure and contacting the plurality of channel layers, and a contact plug connected to the source/drain region. The source/drain region includes a first epitaxial layer disposed on the active region and extending to contact the plurality of channel layers, second epitaxial layers disposed on the first epitaxial layer, each including impurities in a first concentration, and doping layers stacked alternately with the second epitaxial layers, each including the impurities in a second concentration higher than the first concentration.