At least one isolation trench formed in a layer stack including substrate, channel, and upper gate layers define a channel in the channel layer. Lateral etching from the isolation trench(es) can form lateral cavities in the substrate and upper gate layer to substantially simultaneously form self-aligned lower and upper gates. The lower gate undercuts the channel, the upper gate is narrower than the channel, and a source and a drain can be formed on opposed ends of the channel. As a result, source-drain capacitance and gate-drain capacitance can be reduced, increasing speed of the resulting FET.