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. <P> 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. <P> The wide temperature range results from an avantageous circuit structure combined with the SIMOX technology. <P> 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.