A method includes providing a semiconductor structure comprising a varactor region and a field effect transistor region. The varactor region includes a body region in a semiconductor material that is doped to have a first conductivity type. A gate-first process is performed by forming a gate stack over the semiconductor structure. The gate stack includes a layer of gate insulation material and a layer of work function adjustment metal positioned over the layer of gate insulation material. The gate stack is patterned to define a first gate structure over the varactor region and a second gate structure over the field effect transistor region. A source region and a drain region are formed in the field effect transistor region adjacent the second gate structure. The source region and the drain region are doped to have a second conductivity type opposite to the first conductivity type.