To provide a method for manufacturing a DMOS type transistor which can shorten the time of diffusion required for forming a body diffused layer and reduce the influence on the concentration profile of a channel stopper.

An N- type area 121 as a drift area of a DMOS transistor and an N- type 122 as the other element area thereof are formed in a silicon substrate 11. A P+ area 13 beneath an element isolation insulating film 14 is a channel stopper. The DMOS transistor is processed by a gate oxidizing step (for a gate oxide film 15) and a gate electrode 16 is patterned. Next, a resist 18 is formed and P+ type body diffused layer 17 is formed. In this case, a source region is formed by a mask including a gate electrode that is formed later adjacent to the gate electrode 16 and an offset distance can be obtained, so that a time of diffusion required for forming the P+ type body diffused layer 17 may be about the duration of extending it adjacent to the end part of the gate electrode 16.