Structures for a Hall sensor and methods of forming a structure for a Hall sensor. The structure includes a semiconductor body having a top surface and a sloped sidewall defining a Hall surface that intersects the top surface. The structure further includes a well in the semiconductor body and multiple contacts in the semiconductor body. The well has a section positioned in part beneath the top surface and in part beneath the Hall surface. Each contact is coupled to the section of the well beneath the top surface of the semiconductor body.