Transistors, such as field effect transistors (FETs), having high breakdown voltages (e.g., above about 15, and in some applications to about 80 volts or greater) may be incorporated into integrated circuitry. The transistors having high breakdown voltages may be referred to as high-voltage transistors, meaning that the transistors are configured to tolerate high voltages (e.g., above 15 volts).
One technique for creating a high-voltage transistor uses a lightly-doped diffusion region (LDD region) between the drain and gate of the transistor. This region is an active area of the transistor, and is sometimes referred to as a drain extension region. One class of devices utilizing LDD regions are Reduced Surface Field Devices (RESURF) devices.
The breakdown voltage of a high-voltage transistor may be related to the length of the transistor, with longer transistors having higher breakdown voltages. A difficulty encountered in fabricating high-voltage transistors having high breakdown voltages is that such may consume a substantial amount of semiconductor real estate. A continuing goal of integrated circuit fabrication is to reduce the amount of semiconductor real estate consumed by individual devices in order to increase circuit density. Accordingly, it is desired to develop new architectures of high-voltage transistors.