Designs for radiation hardening CMOS devices and integrated circuits using shallow trench isolation (STI) improve total ionizing dose (TID) radiation response by reducing the leakage currents from source to drain associated with corners and sidewalls of trench insulator edges passing under the gate in an NMOS device while maintaining high breakdown voltage. A silicide block pattern is used in combination with pullback of N+ source and drain regions from at least a portion of these edges of the active region. Additional p-type implants along these edges further increase parasitic threshold voltages and enhance radiation hardness. A process for fabricating devices and integrated circuits incorporating these features is also provided. These techniques and processes are applied to exemplary low-voltage NMOS transistors having straight gates and to high-voltage annular-gate devices, as well as to device-to-device isolation in integrated circuits.