Semiconductor devices and manufacturing method of the same are disclosed. A semiconductor device includes a substrate, a p-type MOS transistor, an n-type MOS transistor and a cured flowable oxide layer. The substrate includes a first region and a second region. The p-type MOS transistor is in the first region. The n-type MOS transistor is in the second region. The cured flowable oxide layer covers the p-type MOS transistor and the n-type MOS transistor, wherein a first strain of the cured flowable oxide layer applying to the p-type MOS transistor is different from a second strain of the cured flowable oxide layer applying to the n-type MOS transistor, and the difference therebetween is greater than 0.002 Gpa.