N-type and a manufacturing method mosfet

The invention discloses an N type MOSFET and a manufacturing method thereof. The manufacturing method of the N type MOSFET includes following steps that: a source region and a drain region are formed in a semiconductor substrate; an interfacial oxide layer is formed on the semiconductor substrate; a high K gate dielectric is formed on the interfacial oxide layer; a first metal gate layer is formed on the high K gate dielectric; a doping agent is implanted in the first metal gate layer through conformal doping; and annealing is performed so as to change the effective work function of a gate stack layer, wherein the gate stack layer includes the first metal gate layer, the high K gate dielectric and the interfacial oxide layer.