An adjustable resistor formed on a first insulating layer of a substrate, including: a first polysilicon layer covered with a second insulating layer of a first thickness, except in a region where the first polysilicon layer is covered with a thin insulator layer of a second thickness smaller than the first thickness; a second polysilicon layer covering the second insulating layer and the thin insulator layer; on each side of the second insulating layer and at a distance from it, a first and a second conductive vias providing access to the terminals of the resistor on the first polysilicon layer; and a third conductive via providing access to a contacting area on the second polysilicon layer.