Semiconductor device and method of fabricating the same

Abstract

Disclosed are a semiconductor device and a method of fabricating the same. The semiconductor device includes an active pattern on a substrate, a device isolation layer provided on the substrate to define the active pattern, a pair of source/drain patterns on the active pattern and a channel pattern therebetween, the channel pattern including semiconductor patterns which are stacked and are spaced apart from each other, a gate electrode crossing the channel pattern, and a gate spacer on a side surface of the gate electrode. The gate spacer located on the device isolation layer includes an upper portion with a first thickness and a lower portion with a second thickness. The second thickness is larger than the first thickness, and the lower portion of the gate spacer is located at a level lower than the uppermost one of the semiconductor patterns.