Trench-gate semiconductor devices and their manufacture

Abstract

A device termination structure, and/or a gate bus-bar structure, and/or other end structure is provided for at least one group of cells in a cellular trench-gate semiconductor device, for example a power MOSFET. In this end structure, a conductive layer ( ), for example of polysilicon gate material, extends on an intermediate insulating layer ( ) over a higher-doped (P+) end region ( ) of the channel-accommodating region ( ). This insulating layer ( ) comprises an area ( ) of a trench-etch mask ( ), preferably comprising silicon nitride, that is of greater thickness than the gate dielectric layer ( ). A window ( ) extends through the trench-etch mask ( ) at a location where an end trench ( ) extends into the P+ region ( ). The end trench ( ) is an extension of the insulated gate trench ( ) into the P+ region ( ) and accommodates an extension ( ) of the trench-gate ( ). The conductive layer ( ) is connected to the trench-gate extension ( ) via the window ( ). The lateral extent of the conductive layer ( ) terminates in an edge ( ) that is defined on the trench-etch mask ( ).