Microelectronic devices have a semiconductor/conducting polymer interface are disclosed. The conducting polymer may be electrically contacted in a manner to assure that it remains exposed to the environment. If the environment is an inert electrolyte to which additional electrodes are contacted, the conducting polymer can be electrochemically oxidized or reduced to control its electrochemical potential and a tunable (variable barrier) diode results. This tunable diode is a device that rectifies current like a traditional diode, but unlike traditional diodes, the effective barrier height of the tunable diode can be actively controlled. This control can be an element of an active device or a means for fabricating fixed barrier diodes with controlled barrier heights. Alternatively, the environment can contain an analyte to be sensed, either directly or through a mediating layer. The electrical characteristics (e.g. current-voltage or capacitance voltage) of the semiconductor/conducting polymer interface can be used to sense the analyte if it induces a change in the electrochemical potential of the conducting polymer.