A Novel Lateral DMOS Transistor With H-Shape Shallow-Trench-Isolation Structure

A novel Lateral Double-diffused MOS (LDMOS) with an H-shape shallow-trench-isolation (STI) structure is experimentally proposed in this brief. The H-shaped STI can enhance the dielectric reduced-surface-field effect to the n-drift region from multiple directions, making the n-drift deplete more adequately. In this manner, the peak electrical field and the impact ionization rate along the device surface under high drain voltage are clearly decreased, while an additional short current path near the device surface can still be retained. As a result, when the 52-V breakdown voltage is kept, a competitive specific ON-resistance (R
_ON,sp
) of 23.9 mQ · mm
²
is experimentally achieved using a 0.18-μm BCD process, representing a decrease of 10.5% and 15.9% compared with the conventional split-STI LDMOS and full-STI LDMOS, respectively. The idea can also be generalized to more advanced process nodes.