A method for manufacturing a semiconductor device includes forming a first source/drain region in a substrate. A core channel region is formed on the first source/drain region. A barrier layer is formed on the core channel region. A shell is formed lining sidewalls of the core channel region and sidewalls and top surface of the barrier layer. The shell includes a channel portion in contact with the core channel region and a barrier portion in contact with the barrier layer. A second source/drain region is formed above the shell. A first gate electrode is formed to surround the channel portion of the shell. A conduction energy band of the channel portion of the shell is aligned with a conduction energy band of the barrier portion of the shell.