A transistor structure includes a channel disposed between a source and a drain; a gate conductor disposed over the channel and between the source and the drain; and a gate dielectric layer disposed between the gate conductor and the source, the drain and the channel. In the transistor structure a lower portion of the source and a lower portion of the drain that are adjacent to the channel are disposed beneath and in contact with the gate dielectric layer to define a sharply defined source-drain extension region. Also disclosed is a replacement gate method to fabricate the transistor structure.