Abstract The turn-on and conduction mechanisms of a p-channel compensated MOSFET are discussed. Depending on the implantation and back-bias conditions, two distinct modes of operation occur, each with its own characteristic threshold voltage and conductance relations. In addition, major factors influencing punch-through and the associated subthreshold characteristics have been taken into account. The effect of inversion in the compensating p-layer on the gate capacitance is shown. Experimental data verify the theoretical results presented. Consequences of typical device properties for CMOS modelling are discussed.