SEMICONDUCTOR DEVICE INCLUDING AN ACTIVE PATTERN

A semiconductor device includes: a substrate including an active pattern; a first channel structure overlapping the active pattern; a gate electrode including an electrode portion between the active pattern and the first channel structure; a semiconductor layer contacting the first channel structure; and a source/drain pattern contacting the first channel structure, wherein the first channel structure includes: a first upper channel layer; a first lower channel layer; and a first intervening channel layer disposed between the first upper channel layer and the first lower channel layer, wherein the semiconductor layer contacts a sidewall of the first upper channel layer, a sidewall of the first lower channel layer, and a sidewall of the first intervening channel layer, and wherein the semiconductor layer and the first intervening channel layer include a semiconductor material that is different from a semiconductor material of the first upper channel layer and the first lower channel layer.