A transistor structure is provided in the present invention. The transistor structure includes: a substrate comprising a P-type well, a gate disposed on the P-type well, a first spacer disposed on the gate, an N-type source/drain region disposed in the substrate at two sides of the gate, a silicon cap layer covering the N-type source/drain region, a second spacer around the first spacer and the second spacer directly on and covering a portion of the silicon cap layer and a silicide layer disposed on the silicon cap layer.