Abstract
A semiconductor device includes a barrier layer, a dielectric layer, a first spacer, a second spacer, and a gate. The dielectric layer is disposed on the barrier layer and defines a first recess. The first spacer is disposed on the barrier layer and within the first recess. The second spacer is disposed on the barrier layer and within the first recess. The first and second spacers are spaced apart from each other by a top surface of a portion of the barrier layer. The top surface of the portion of the barrier layer is recessed. The gate is disposed on the barrier layer, the dielectric layer, and the first and second spacers, in which the gate has a bottom portion located between the first and second spacers and making contact with the top surface of the portion of the barrier layer.