A method for forming a group III-V semiconductor channel region in a transistor is provided herein. The method includes exposing a substrate including an oxide layer to a first plasma to treat the oxide layer, exposing the treated oxide layer to a second plasma to convert the oxide layer to an evaporable layer, evaporating the evaporable layer to expose a group III-V semiconductor material surface, and exposing the group III-V semiconductor material surface to an oxygen containing gas to oxidize the group III-V semiconductor material. The processes may be repeated until a recessed depth having a predetermined depth is formed. A group III-V semiconductor channel is then formed in the predetermined recessed depth. The control of the height of the group III-V semiconductor channel is improved.