Disclosed are a semiconductor structure and method of forming the structure. The structure includes a field effect transistor (FET) with a channel region between source/drain regions that extend through a semiconductor layer and into an insulator layer, that include a first portion in the insulator layer, and a second portion on the first portion in the semiconductor layer and, optionally, extending above the semiconductor layer. The first portion is relatively wide, includes a shallow section below the second portion, and a deep section adjacent to the channel region and overlayed by the semiconductor layer. The uniquely shaped first portion boosts saturation current to be boosted to allow the height of the second portion to be reduced to minimize overlap capacitance. Optionally, each source/drain region includes multiple semiconductor materials including a stress-inducing semiconductor material grown laterally from the semiconductor layer to improve charge carrier mobility in the channel region.