Novel STI scheme and layout design to suppress the kink effect in LDMOS transistors

Two simple methods to suppress anomalous subthreshold conduction, the so-called ‘kink effect’ of lateral double-diffused MOS (LDMOS), were demonstrated. According to TSUPREM-4 simulation and calculation results, LDMOSFETs were more prone to subthreshold kinks than standard CMOSFETs because of the oxidation-enhanced-diffusion (OED) effect and small gate capacitor. The fringing electrical field, which arises from a shallow trench isolation (STI) divot, was remarkably eliminated by the improved isolation scheme. A novel device layout was designed so that the channel dopant segregation can be automatically compensated without any extra processing steps.