A method for forming source/drain regions in a semiconductor device and a semiconductor device including source/drain regions formed by the method are disclosed. In an embodiment, a method includes etching a semiconductor fin to form a first recess, the semiconductor fin defining sidewalls and a bottom surface of the first recess, the semiconductor fin extending in a first direction; forming a source/drain region in the first recess, the source/drain region including a single continuous material extending from a bottom surface of the first recess to above a top surface of the semiconductor fin, a precursor gas for forming the source/drain region including phosphine (PH3) and at least one of arsine (AsH3) or monomethylsilane (CH6Si); and forming a gate over the semiconductor fin adjacent the source/drain region, the gate extending in a second direction perpendicular the first direction.