A trench DMOS transistor employing trench contacts has overvoltage protection for prevention of shortage between gate and source, comprising a plurality of first-type function trenched gates, at least one second-type function trenched gate and at least two third-type function trenched gates extending through body regions and into an epitaxial layer. The first-type function trenched gates are located in active area surrounded by a source region encompassed in the body region in the epitaxial layer for current conduction. The second-type function trenched gates are disposed underneath a gate metal with a gate trenched contacts filled with metal plug for gate metal connection. The third type function trenched gates are disposed directly and symmetrically underneath ESD trenched contact areas of anode and cathode in an ESD protection diode, serving as a buffer layer for prevention of gate-body shortage.