An insulated gate field effect transistor has a drain region (2,4), a body region (6) of opposite conductivity type and a source region (8) and an insulated gate (14) extending laterally over the body region (6), defining a channel region (30) extending in the body region (6) from a source end adjacent to the source region (8) to a drain end adjacent to a drain end part (26) of the drain region (4). A conductive shield plate (22) is provided adjacent to the drain end for shielding the gate. Embodiments include a shield plate extension (32) extending over the drain region from the shield plate (22) towards the gate (14).