A vertical Hall effect sensor comprising: a semiconductor wafer having a first conductivity type; a plurality of semiconductive electrodes (118, 120A, 120B, 122A, 122B) disposed on the semiconductor wafer, the plurality of semiconductive electrodes having the first conductivity type, comprising: a source electrode; a first sensing electrode and a second sensing electrode, arranged such that the source electrode is between the first sensing electrode and the second sensing electrode; and a first drain electrode and a second drain electrode, arranged such that the first sensing electrode, second sensing electrode, and source electrode are between the first drain electrode and the second drain electrode; a plurality of electrically floating semiconductor fingers (124A-124D) disposed on the semiconductor wafer and interdigitated with the plurality of semiconductive electrodes, the semiconductor fingers having a second conductivity type; and at least one semiconductor blanket disposed at a first depth below at least one of the plurality of semiconductor electrodes (118, 120A, 120B, 122A, 122B) in the semiconductor wafer; characterised in that: the width of each electrically floating semiconductor finger (124A-124D) is between 5% and 12% of the semiconductor wafer thickness; and the first depth is less than a depth of depletion regions beneath the semiconductor fingers. a semiconductor wafer having a first conductivity type; a plurality of semiconductive electrodes (118, 120A, 120B, 122A, 122B) disposed on the semiconductor wafer, the plurality of semiconductive electrodes having the first conductivity type, comprising: a source electrode; a first sensing electrode and a second sensing electrode, arranged such that the source electrode is between the first sensing electrode and the second sensing electrode; and a first drain electrode and a second drain electrode, arranged such that the first sensing electrode, second sensing electrode, and source electrode are between the first drain electrode and the second drain electrode; a source electrode; a first sensing electrode and a second sensing electrode, arranged such that the source electrode is between the first sensing electrode and the second sensing electrode; and a first drain electrode and a second drain electrode, arranged such that the first sensing electrode, second sensing electrode, and source electrode are between the first drain electrode and the second drain electrode; a plurality of electrically floating semiconductor fingers (124A-124D) disposed on the semiconductor wafer and interdigitated with the plurality of semiconductive electrodes, the semiconductor fingers having a second conductivity type; and at least one semiconductor blanket disposed at a first depth below at least one of the plurality of semiconductor electrodes (118, 120A, 120B, 122A, 122B) in the semiconductor wafer; characterised in that: the width of each electrically floating semiconductor finger (124A-124D) is between 5% and 12% of the semiconductor wafer thickness; and the first depth is less than a depth of depletion regions beneath the semiconductor fingers. the width of each electrically floating semiconductor finger (124A-124D) is between 5% and 12% of the semiconductor wafer thickness; and the first depth is less than a depth of depletion regions beneath the semiconductor fingers.