A semiconductor device includes first channel layers disposed over a substrate, a first source/drain region disposed over the substrate, a gate dielectric layer disposed on each of the first channel layers, a gate electrode layer disposed on the gate dielectric. Each of the first channel layers includes a semiconductor wire made of a first semiconductor material. The semiconductor wire passes through the first source/drain region and enters into an anchor region. At the anchor region, the semiconductor wire has no gate electrode layer and no gate dielectric, and is sandwiched by a second semiconductor material.