A method and structure for suppressing band-to-band tunneling current in a semiconductor device having a high-mobility channel material includes forming a channel region adjacent to and in contact with one of a source region and a drain region. A tunnel barrier layer may be formed such that the tunnel barrier layer is interposed between, and in contact with, the channel region and one of the source region and the drain region. In some embodiments, a gate stack is then formed over at least the channel region. In various examples, the tunnel barrier layer includes a first material, and the channel region includes a second material different than the first material. In some embodiments, the semiconductor device may be oriented in one of a horizontal or vertical direction, and the semiconductor device may include one of a single-gate or multi-gate device.