The invention provides a semiconductor device, including: a semiconductor device includes: a substrate having a first conductivity type, including: a body region having the first conductivity type; a source region formed in the body region; a drift region having a second conductivity type adjacent to the body region, wherein the first conductivity type is opposite to the second conductivity type; and a drain region formed in the drift region; a trench formed in the substrate between the body and drift regions; a gate dielectric layer disposed adjacent to the trench; a liner lining the trench and adjoining with the gate dielectric layer; and a gate electrode formed over the gate dielectric layer and extending into the trench.