The present disclosure generally relates to junction diode isolation in an integrated circuit die. In an example, a semiconductor device includes a diode and a transistor. The diode is in a semiconductor substrate. The diode includes an anode region, an n-type well, a cathode region, and an n-type buried layer each in the semiconductor substrate. The cathode region is in the n-type well. The n-type buried layer extends from the n-type well laterally towards the anode region. The transistor includes a source region and a drain region in the semiconductor substrate. The source and drain regions are between the anode and cathode regions. A lateral distance is between the cathode region and a lateral edge of the n-type buried layer proximate the anode region. The lateral distance is parallel to a channel length of the transistor. The lateral distance decreases from proximate the transistor to distal from the transistor.