Field programmable logic devices provide a cost and time efficient way to create new microcontroller designs. These qualities are particular useful and desirable for high temperature applications in hostile environments above 250 °C. Starting from summarizing the present state-of-the-art in SIMOX high temperature developement the presented work introduces HTPAL devices as an example of a new class of programmable logic devices. These class is characterized by a range of features that were not available in am similar combination before: a wide temperature range from -50 °C up to 250 °C and above, high resistance against ionizing radiation, flexible and permanent field programmability by the end user. The wide temperature range results from an avantageous circuit structure combined with the SIMOX technology. Permanent field programmability is achieved by using a new One-time-programmable (OTP) MOSFET device, called a TOXFET. The new device consists of a high voltage NMOS transistor combined with a thin tunnel oxide to initially insulate the drain lead from the transistor structure.