A bipolar junction transistor may act as a select device for a semiconductor memory. The bipolar junction transistor may be formed of a stack of base and collector layers. Sets of parallel trenches are formed in a first direction down to the base and in a second direction down to the collector. The trenches may be used to form local enhancement implants into the exposed portion of the base and collector in each trench. As a result of the local enhancement implants, in some embodiments, leakage current may be reduced, active current capability may be higher, gain may be higher, base resistance may be reduced, breakdown voltage may be increased, and parasitic effects with adjacent junctions may be reduced.