Patent attributes
A HEMT-type field-effect semiconductor device has a main semiconductor region comprising two layers of dissimilar materials such that a two-dimensional electron gas layer is generated along the heterojunction between the two layers. A source and a drain electrode are placed in spaced positions on the main semiconductor region. Between these electrodes, with spacings therefrom, an insulator is provided with is made from a material capable of developing a stress to reduce carrier concentration in neighboring part of the two-dimensional electron gas layer, creating a discontinuity in this layer. A gate electrode overlies the insulator via a piezoelectric layer which is made from a material capable of developing, in response to a voltage applied to the gate electrode, a stress for canceling out the stress developed by the insulator. Thus the device is physically held off by the action of the insulator while no voltage is being impressed to the gate electrode and, upon voltage application thereto, piezoelectrically turns on by the action of the piezoelectric layer. The turn-on resistance of the device is relatively low as the insulator occupies only part of the source-drain spacing.
