Dual SOI film thickness for body resistance control

A method of forming semiconductor devices, comprising the steps of:

• forming first silicon regions on a buried oxide (BOX) layer of a silicon-on-insulator (SOI) precursor, the first silicon region having a first thickness;
• forming second silicon regions on the BOX layer having a second thickness greater than the first thickness;
• isolating the first and second silicon regions from each other;
• and
• forming floating-body devices in the first regions and body-tied devices in the second regions;
• wherein the step of isolating includes forming shallow trench isolation (STI) regions on the BOX layer;
• comprising forming recessed portions and unrecessed portions in the BOX layer;
• wherein the steps of forming first and second silicon regions include depositing silicon in the recessed portions and on the unrecessed portions of the BOX layer.