A New E-SIMOX high voltage device structure with Shielding Trench (ST) and its breakdown mechanism with the self-adapted interface charge are proposed in this paper. Cased on the full continuity principle of electric displacement, the interface charges enhance the vertical electric field of buried oxide remarkably and reduce the vertical electric field of Si layer, which shield Si layer from high electric field. The vertical electric field and breakdown characteristic is researched for different device structure parameters with ST by 2-D device simulator. The electric field of buried oxide increases from below 100V/μm to about 600V/μm. It breaks through the limitation of breakdown voltage of normal SOI device and expands the application field of SOI device.
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