Abstract: A novel SOI high voltage device structure with a shielding trench and its breakdown mode with a self-adapted interface charge are proposed.Interface charges that change with the drain voltage are introduced in the shielding trench.Interface charges enhance the vertical electric field of the buried layer and reduce that of the top Si layer simultaneously.Furthermore,they also modulate the surface electric field.So, interface charges shield the top Si layer from a high electric field.The breakdown voltage and electric field profile are researched for different device parameters for a ST structure by using a 2D device simulator.It is shown that the electric field of buried oxide increases from about 3ESi to 600V/μm.It breaks through the limitation of the sustained voltage of the buried oxide layer of a normal SOI device and enhances the breakdown voltage of the SOI device remarkably.

Key words: shielding trench, self-adapted interface charge, modulate, vertical electric field, breakdown voltage