A method of forming a semiconductor device structure includes providing a substrate with a semiconductor-on-insulator (SOI) configuration, the SOI substrate comprising a semiconductor layer formed on a buried oxide (BOX) layer which is disposed on a semiconductor bulk substrate, forming trench isolation structures delineating a first region and a second region within the SOI substrate, removing the semiconductor layer and the BOX layer in the first region for exposing the semiconductor bulk substrate within the first region, forming a first semiconductor device with an electrode in and over the exposed semiconductor bulk substrate in the first region, forming a second semiconductor device in the second region, the second semiconductor device comprising a gate structure disposed over the semiconductor layer and the BOX layer in the second region, and performing a polishing process for defining a common height level to which the electrode and the gate structure substantially extend.