Provided is a semiconductor device using a p-type oxide semiconductor layer and a method of manufacturing the same. The device includes the p-type oxide layer formed of at least one oxide selected from the group consisting of a copper(Cu)-containing copper monoxide, a tin(Sn)-containing tin monoxide, a copper tin oxide containing a Cu—Sn alloy, and a nickel tin oxide containing a Ni—Sn alloy. Thus, transparent or opaque devices are easily developed using the p-type oxide layer. Since an oxide layer that is formed using a low-temperature process is applied to a semiconductor device, the manufacturing process of the semiconductor device is simplified and manufacturing costs may be reduced.