A vFET includes a first impurity region doped with first impurities at an upper portion of the substrate. A first diffusion control pattern is formed on the first impurity region. The first diffusion control pattern is configured to control the diffusion of the first impurities. A channel extends in a vertical direction substantially orthogonal to an upper surface of the substrate. A second impurity region is doped with second impurities on the channel. A second diffusion control pattern is between the channel and the second impurity region. The second diffusion control pattern is configured to control the diffusion of the second impurities. A gate structure is adjacent to the channel.