This paper deals with the development of state-of-the-art ultra low power (ULP) consumption hotplates to be used as metal oxide gas sensor substrates. Several types of ULP devices, differing in shape and size, have been fabricated with the same front-side bulk silicon micromachining technology. Details on the device design and on the fabrication processes are provided. The ULP hotplates functional behavior was thoroughly investigated. Typical results on measurements of the hotplate temperature versus applied power are reported. A very satisfactory value of 8.9 mW at 400degC can be highlighted. Transient temperature responses and evaluation of the hotplate thermal time constant were also carried out.