A method of making a semiconductor device includes forming shallow trench isolation structures in a semiconductor device layer. The shallow trench isolation structures are U- or O- shaped enclosing field regions formed of the semiconductor device layer which is doped and/or silicided to be conducting. The semiconductor device may include an extended drain region or drift region and a drain region. An insulated gate may be provided over the body region. A source region may be shaped to have a deep source region and a shallow source region. A contact region of the same conductivity type as the body may be provided adjacent to the deep source region. The body extends under the shallow source region to contact the contact region.