MOSFET interface state densities of different technologies

In order to determine the relationship between channel length and interface state density, a test structure with sets of n-channel and p-channel transistors having different channel lengths was used. The transistors had the same width and were situated side by side. A transistor with a gate in a trench was also tested. Charge pumping measurements showed conventional nMOSFETs to have the lowest interface state density, followed by conventional pMOSFETs, LDD nMOSFETs, and trench channel transistors. No increase of interface state density was found for submicron MOSFETs in comparison with long-channel transistors.