Abstract The quality of the semiconductor–barrier interface plays a pivotal role in the demonstration of high quality reproducible quantum dots for quantum information processing. In this work, we have measured SiMOSFET Hall bars on undoped Si substrates in order to investigate the device quality. For devices fabricated in a full complementary metal oxide semiconductor (CMOS) process and of very thin oxide below a thickness of 10 nm, we report a record mobility of 17.5 × 10³ cm² V⁻¹ s⁻¹ indicating a high quality interface, suitable for future qubit applications. We also study the influence of gate materials on the mobilities and discuss the underlying mechanisms, giving insight into further material optimization for large scale quantum processors.