Semiconductor device

Abstract

A semiconductor device includes a substrate; an active region extending in a first, horizontal, direction on the substrate, and including a first active pattern at a first height above a bottom surface of the substrate in a vertical direction and having a first width in a second, horizontal, direction, a second active pattern having a second width in the second direction different from the first width, and a transition active pattern connecting the first active pattern to the second active pattern; gate structures intersecting the active region each gate structure extending in the second direction across the substrate; source/drain regions disposed on sides of the gate structures, and including a first source/drain region disposed on the first active pattern, a second source/drain region disposed on the second active pattern, and a transition source/drain region disposed on the transition active pattern. Each of the source/drain regions is disposed on the active region and includes a first epitaxial layer having a recessed upper surface and a second epitaxial layer disposed on the first epitaxial layer, at a second height above a bottom surface of the substrate in a vertical direction, a first sidewall thickness of the first epitaxial layer of the first source/drain region in the first direction is different from a second sidewall thickness of the first epitaxial layer of the second source/drain region in the first direction, at the second height, thicknesses of opposing sidewalls of the first epitaxial layer of the transition source/drain region in the first direction are different, and a vertical level of a lowermost end of the second epitaxial layer of the first source/drain region, a vertical level of a lowermost end of the second epitaxial layer of the second source/drain region, and a vertical level of a lowermost end of the second epitaxial layer of the transition source/drain region are different from each other.