Field-effect controlled transistor devices with an insulated gate electrode are widely used as electronic switches in automotive, industrial, household or consumer electronic applications. These transistor devices are available with voltage blocking capabilities of between several volts and several kilovolts. A field-effect controlled transistor device with an insulated gate electrode includes a source region of a first doping type (conductivity type) in a body region of a second doping type complementary to the first doping type. A drift region of the first conductivity type adjoins the body region and is located between the body region and a drain region. The gate electrode is adjacent the body region, dielectrically insulated from the body region by a gate dielectric, and serves to control a conducting channel in the body region between the source region and the drift region. This type of transistor device is commonly referred to as MOS (Metal Oxide Semiconductor) transistor device although the gate electrode not necessarily includes a metal and the gate dielectric not necessarily include an oxide. Examples of an MOS transistor device include a MOSFET (Metal Oxide Field-Effect Transistors), and an IGBT (Insulated Gate Bipolar Transistors)
One challenge in the design of MOS transistor devices is to achieve a low area-specific on-resistance (R0N·A) at a given voltage blocking capability. This area-specific on-resistance is the product of the ohmic resistance (R0N) of the transistor device in an on-state and the chip area (A).
With an improvement in the area-specific on-resistance, at a given on-resistance and a given voltage blocking capability, the chip area (chip size) becomes smaller. A reduction of the chip area also results in a reduction of capacitances, such as gate-source capacitances and gate-drain capacitances. Those capacitances affect the switching speed of the transistor device. The switching speed is a measure of how fast the transistor device switches from an on-state to an off-state, and in the other direction. Reduced capacitances cause the transistor device to switch faster. A fast switching of the transistor devices is associated with steep edges of a voltage across the transistor device, a voltage across a load operated by the transistor device, or a current through the transistor device. Those steep edges can be critical with regard to electromagnetic interference.
It may therefore be desirable in a transistor device with a low on-resistance to soften the switching behavior.