An LDMOS transistor (100) on a substrate (70a, 70b) of a first conductivity type, comprises a source region (10) with a source portion (73) and a drain region (12). The source portion and drain region are of a second conductivity type opposite to the first conductivity type and are mutually connected through a channel region (28) in the substrate over which a gate electrode (14) extends. The drain region comprises a drain contact region (16) and a drain extension region (15) which extends from the channel region (28) towards the drain contact region. The drain contact region is electrically connected to a top metal layer (22) by a drain contact (20), and a poly-Si drain contact layer (80) is arranged as a first contact material in between the drain contact region and the drain contact in a contact opening (51) of a first dielectric layer (52) deposited on the surface of the drain region. The poly-Si drain contact layer comprises a dopant element of the second conductivity type which is diffused therefrom through annealing to form said drain contact region.