Trench j-MOS power field-effect transistors

A normally-on MOSFET structure called j-MOS for automotive electronic systems applications is discussed. These devices are built on silicon-on-insulator (SOI) and in bulk silicon and can be integrated as a smart power circuit element. The lowest on-resistance j-MOS device is built in an ideal trench configuration in bulk silicon and can be operated in either a three-terminal or a four-terminal mode. When operated in accumulation, a specific on-resistance of 0.8 mΩcm² is reported. This low on-resistance is attributed to the combination of bulk conduction and surface accumulation, as well as to the details of the electron current flow in the channel. A factor of two superiority is reported in on-resistance over a trench DMOS structure for a given drain blocking voltage and feature size. In the four-terminal mode, a high transconductance, 290 S/cm², is achieved by controlling the voltage on the small junction in the gate. In the three-terminal mode, mixed pentode-triode drain characteristics are exhibited. Response times are comparable to those of a junction FET. This simple self-aligned structure could be useful in power switching and control applications