Silicon photo-multipliers (SiPM) consist in matrices of tiny, passive quenched avalanche photo-diode cells connected in parallel via integrated resistors and operated in Geiger mode. Novel types of SiPM are being developed at FBK-IRST (trento, Italy). Despite their classical shallow junction n-on-p structure the devices are unique in their enhanced photo-detection efficiency (PDE) for short-wavelengths and in their low level of dark rate and excess noise factor. After a summary of the extensive SiPM characterization we will focus on the study of PDE and the single photon timing resolution. (C) 2007 Elsevier B.V. All rights reserved.