A MOS varactor is formed having a gate electrode comprising at least two abutting oppositely doped regions shorted together, in which the two regions are implanted simultaneously with source/drain implants for first and second types of transistor; at least one contact to a lower electrode is also formed simultaneously with the source/drain implants for the first type of transistor; the varactor insulator is formed simultaneously with the gate insulator for one type of transistor; and the lower electrode is formed simultaneously with a well for the first type of transistor, so that no additional mask is required.