Compared with bulk-silicon technology, silicon-on-insulator (SOI) technology possesses many advantages but it is inevitable that the buried silicon dioxide layer also thermally insulates the metal–oxide–silicon field-effect transistors (MOSFETs) from the bulk due to the low thermal conductivity. One of the alternative insulator to replace the buried oxide layer is aluminum nitride (AlN), which has a thermal conductivity that is about 200 times higher than that of SiO₂ (320 W·m⁻¹·K⁻¹ versus 1.4 W·m⁻¹·K⁻¹). To investigate the self-heating effects of small-size MOSFETs fabricated on silicon-on-aluminum nitride (SOAN) substrate, a two-dimensional numerical analysis is performed by using a device simulator called MEDICI run on a Solaris workstation to simulate the electrical characteristics and temperature distribution by comparing with those of bulk and standard SOI MOSFETs. Our study suggests that AlN is a suitable alternative to silicon dioxide as a buried dielectric in SOI and expands the applications of SOI to high temperature conditions.