A BiCMOS substrate includes a bipolar area having a buried carrier layer, and a deep trench isolation (DTI) trench extending into the buried carrier layer to form a surface well implant above a buried well implant within the DTI trench, the buried well implant being the buried carrier layer portion within the DTI trench. A floating gate is disposed on the carrier well. Optionally, a high voltage control gate is formed of a stack of the buried well implant and the surface well implant within the DTI trench. Optionally, a poly layer formed of a bipolar process base poly layer is disposed on the floating gate. Optionally, a shallow well isolation region is formed on the substrate, a floating gate is disposed on the shallow well region, and an overlaying control gate, formed of a bipolar process base poly, is disposed above the floating gate.