A spin transistor includes a source electrode, a drain electrode, and a gate electrode on a semiconductor substrate. At least one of the source electrode and the drain electrode includes a semiconductor region and a magnetic layer. The semiconductor region is formed in the semiconductor substrate. The magnetic layer is formed on the semiconductor region, and contains a crystalline Heusler alloy containing at least one of cobalt (Co) and iron (Fe). The semiconductor region and the magnetic layer contain the same impurity element.