The invention relates to a manufacturing method of a lateral double-diffused
transistor. The manufacturing method comprises the following steps that: a first liner
oxide layer is formed on the surfaceof a substrate, and a P-type well region and an N-type well region which are separated from each other are formed on the substrate; an N-type drift region is formed in the substrate through the opening of a first
hard mask, wherein the N-type drift region is spaced apart from the P-type well region and adjacent to the N-type well region; a second liner
oxide layer is formed on the N-type drift region and the N-type well region via the opening of the first
hard mask, wherein the second liner
oxide layer has a thickness greater than that of the first liner oxide layer; and a
field oxide layer is formed on the N-type drift region via the opening of a second
hard mask, wherein the second hard
mask blocks a portion of the second liner oxide, wherein the portion of the second liner oxide is adjacent to the P-type well region. According to the manufacturing method, the drift region and the second liner oxide layer are formed through the opening of the first hard
mask, so that the thickness of the edge of the
beak region of the
field oxide layer is increased, and therefore, the
electric field of the substrate below the
beak region is reduced, and the
breakdown voltage of the
transistor iseffectively improved while process cost is saved.