The conventional ion-sensitive field-effect transistor (ISFET) with SiO2 as the insulator of choice has been used as an electrochemical sensor to measure ion concentrations in solutions for many decades. With the ongoing progress in use of silicon nanoribbon (SiNR) FET sensors for fast reliable sensing and the recent demand for pH-sensing technologies in biological applications, it is important to identify the true pH response of the device. However, it has become much more difficult to achieve reliable results across a broad range of pH using SiO2-gated SiNR FET sensors and limitations such as long term drift and hysteresis (also referred to as memory effects) during pH measurements need to be addressed. In this work, we have investigated the electrochemical pH response behavior of silicon oxide-gated SiNR FET sensors and compared it with similar devices (same NR size) but with Al2O3 as the gate oxide. Our studies show that devices passivated with SiO2 show a large hysteresis in the pH response both in acidic and in basic direction, whereas Al2O3 surfaces show slight hysteresis and only in the acidic pH range. Furthermore, in case of SiO2, the total response-time after a pH change appears to be a combination of a fast transient and a slow drift which is related both to the type of oxide and the concentration of the background electrolyte. Consequently, to minimize errors in pH measurements caused by hysteresis and delayed response, we advise performing the measurements at low ionic concentrations and preferably to replace SiO2 by Al2O3 as the gate oxide. In biological applications, we also recommend the integration of an on-chip reference nanoribbon FET for real-time monitoring of problems such as long-term drift and slow response.