A semiconductor fabrication method includes forming a semiconductor structure including source/drain regions disposed on either side of a channel body wherein the source/drain regions include a first semiconductor material and wherein the channel body includes a migration barrier of a second semiconductor material. A gate dielectric overlies the semiconductor structure and a gate module overlies the gate dielectric. An offset in the majority carrier potential energy level between the first and second semiconductor materials creates a potential well for majority carriers in the channel body. The migration barrier may be a layer of the second semiconductor material over a first layer of the first semiconductor material and under a capping layer of the first semiconductor material. In a one dimensional migration barrier, the migration barrier extends laterally through the source/drain regions while, in a two dimensional barrier, the barrier terminates laterally at boundaries defined by the gate module.