Non-planar semiconductor devices having group III-V material active regions with multi-dielectric gate stacks are described. For example, a semiconductor device includes a hetero-structure disposed above a substrate. The hetero-structure includes a three-dimensional group III-V material body with a channel region. A source and drain material region is disposed above the three-dimensional group III-V material body. A trench is disposed in the source and drain material region separating a source region from a drain region, and exposing at least a portion of the channel region. A gate stack is disposed in the trench and on the exposed portion of the channel region. The gate stack includes first and second dielectric layers and a gate electrode.