Abstract: An electrical switch performs multi-polar switching. A HDFET structure has a source (2) at one terminal and two drains (3(a) and 3(b)) providing isolated terminals at the opposite end. The drains (3(a) and 3(b)) are separated by an insulator (8). N+ gates (6, 7) are at each side of a channel (5) linking the source (2) with the drains (3(a), 3(b)). Bias of the gates (6, 7) is controlled to control depletion regions (21, 22) to switch on or off current flow (A, B) between the source (2) and the drains (3(a), 3(b)).