A modified structure of an n-channel lateral double-diffused metal oxide semiconductor (LDMOS) transistor is provided to suppress the rupturing of the gate-oxide which can occur during the operation of the LDMOS transistor. The LDMOS transistor comprises a dielectric isolation structure which physically isolates the region comprising a parasitic NPN transistor from the region generating a hole current due to weak-impact ionization, e.g., the extended drain region of the LDMOS transistor. According to an embodiment of the disclosure, this can be achieved using a vertical trench between the two regions. Further embodiments are also proposed to enable a reduction in the gain of the parasitic NPN transistor and in the backgate resistance in order to further improve the robustness of the LDMOS transistor.