A semiconductor device including at least one variable resistance device is provided. A variable resistance element includes: an ion supply layer having a top, a bottom and a sidewall connecting the top to the bottom; an ion-receiving layer having an inner sidewall connected to at least a portion of the sidewall of the ion supply layer; a gate pattern connected to an outer sidewall of the ion-receiving layer; and a source pattern connected to one of the top or bottom of the ion supply layer, and a drain pattern connected to the other one or the top or bottom of the ion supply layer. A resistance of the ion supply layer is varies depending on an amount of ions supplied from the ion supply layer to the ion-receiving layer in response to a voltage applied to the gate pattern.