In this contribution, new developments on the silicon photomultipliers (SiPM) fabricated at FBK-irst (Trento, Italy) are reported. With respect to the first series of devices produced in 2005/2006, there have been major improvements on both the layout and the technology. Concerning the first aspect we fabricated SiPMs with increased fill factor and with different geometries (square/circular devices, arrays and matrices of SiPMs) to meet the requirements of different applications. Concerning the technology, we identified a process technique able to reduce significantly the dark count rate. In this paper we will describe the main electro-optical characteristics of these devices.