A dolly and a tray and dolly assembly are provided. Specifically, in one embodiment, each of the memory cells in the array of memory cells includes a source, a control gate, and a drain, and is capable of storing at least one bit. The method also includes forming a first trench on the first active region using a first barrier layer and a second substitute gate electrode layer to protect a gate region on the second active region, followed by forming a first work function layer and a first metal gate in the first trench. From the recorded response, the threshold voltage and the average surface doping concentration are determined.