Trench gate power MOSFETs with retrograde body profile

Low specific on-resistance (R_ds,on) and low gate capacitance are essential for trench gate power MOSFETs. In this work, we propose a simple method of retrograde body profile to improve the two parameters simultaneously. The retrograde body MOSFET (RBMOS) is realized by high energy implantation. Because the highest channel concentration is located close to the drain side, the depletion width at the drain side is suppressed, so that the channel length can be shortened greatly without sacrificing punch-through voltage. A low thermal budget and easy trench gate process are additional benefits. A power MOSFET with channel length of 0.4 μm, threshold voltage of 1 V, and breakdown voltage of 32 V is demonstrated. Compared with the conventional device, the specific on-resistance and the figure-of-merit can be improved by 38% and 70%, respectively.