The present invention provides a single-electron transistor device (100). The device (100) comprises a source (105) and drain (110) located over a substrate (115) and a quantum island (120) situated between the source and drain (105, 110), to form tunnel junctions (125, 130) between the source and drain (105, 110). The device (100) further includes a movable electrode (135) located adjacent the quantum island (120) and a displaceable dielectric (140) located between the moveable electrode (135) and the quantum island (120). The present invention also includes a method of fabricating a single-electron device (200), and a transistor circuit (300) that include a single-electron device (310).